In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Ibnul Qayyim [rahimahullaah] said: Muhammad’s [sallal-laahu-alayhi-wasallam] Ummah is not in need of anyone after him; rather the only need they have is someone to convey what he came with. Muhammad’s [sallal-laahu-alayhi-wasallam] message is comprehensive, universal and preserved. This universality, comprehensiveness and preservation is not limited to [any time and place], rather it is comprehensive for those to whom Muhammad [sallal-laahu-alayhi-wasallam] was sent [i.e. the whole world] and likewise with regards to everything that is needed in the fundamental and subsidiary issues of the religion.
Muhammad’s [sallal-laahu-alayhi-wasallam] message is sufficient, all embracing and universal- nothing else is needed besides it. It has not isolated any affair of truth needed by his Ummah in their sciences and deeds. The Messenger of Allaah [sallal-laahu-alayhi-wasallam] did not leave this world until he acquainted his Ummah with everything. He even taught them the etiquettes of using the toilet; the etiquettes of sexual relations; the etiquettes of sleep and after waking up; the etiquettes of eating, drinking and travel.
He acquainted them with the etiquettes of speech and silence; the etiquettes of keeping company with the people and seclusion. He acquainted them with the affairs of illness, good health, poverty and wealth. He acquainted them with all the affairs of life and death. He described Allaah’s throne, the angels, the jinn, the hell fire and the day of judgement in such a manner as if one has seen them with the naked eye. He [sallal-laahu-alayhi-wasallam] informed them about their Lord and His Perfect Names and Attributes, and that Allaah alone is their true object of worship.
He acquainted them with the Prophets of old and their nations – the events that took place between them and their nations – in such a manner as if one was present at that time. He acquainted them with all the means to good and the paths of evil- in general and in detail- which no other prophet informed his nation. He acquainted them with death and what will take place in the grave – either bliss or punishment. He acquainted them with the evidences and proofs of Tawheed [i.e. the oneness of Allaah in His Lordship, Names and Attributes, and that Allaah alone has the right to be worshipped].
He acquainted them with Prophet hood and the affairs of the Afterlife, and he refuted all the sects of disbelief and misguidance. He acquainted them with war strategies- how to confront the enemy, the way to achieve victory and conquests. If only they knew and understood these affairs in the correct manner [i.e. the manner it should be understood], they would not be overcome by their enemy. He acquainted them with the plots of Iblees and the ways through which he approaches them, and the ways to repel those plots and plans. He acquainted them with the soul- its characteristics and faults- in such a manner that they are not in need of anyone else to tell them about it. He taught them how to live their daily lives and had they acknowledged and acted upon this, their worldly affairs would be firmly established. He brought them all the means of success in this life and the next, and they do not need anyone besides him. So how can it be said that the path of Muhammad [sallal-laahu-alayhi-wasallam] is in need of something else outside of it. The reason for such a claim is due to the weak and little understanding of a person. Allaah [The Most High] said:
أَوَلَمْ يَكْفِهِمْ أَنَّا أَنزَلْنَا عَلَيْكَ الْكِتَابَ يُتْلَىٰ عَلَيْهِمْ ۚ إِنَّ فِي ذَٰلِكَ لَرَحْمَةً وَذِكْرَىٰ لِقَوْمٍ يُؤْمِنُونَ
Is it not sufficient for them that We have sent down to you the Book (the Qur’an) which is recited to them? Verily, herein is mercy and a reminder (or an admonition) for a people who believe. [29:51]
Allaah [The Most High] said:
وَنَزَّلْنَا عَلَيْكَ الْكِتَابَ تِبْيَانًا لِّكُلِّ شَيْءٍ وَهُدًى وَرَحْمَةً وَبُشْرَىٰ لِلْمُسْلِمِينَ
And We have sent down to you the Book (the Qur’an) as an exposition of everything, a guidance, a mercy, and glad tidings for those who have submitted themselves (to Allah as Muslims). [16:89]
Allaah [The Most High] said:
يَا أَيُّهَا النَّاسُ قَدْ جَاءَتْكُم مَّوْعِظَةٌ مِّن رَّبِّكُمْ وَشِفَاءٌ لِّمَا فِي الصُّدُورِ وَهُدًى وَرَحْمَةٌ لِّلْمُؤْمِنِينَ
O mankind! There has come to you a good advice from your Lord [i.e. the Qur’an, ordering all that is good and forbidding all that is evil], and a healing for that [disease of ignorance, doubt, hypocrisy and differences, etc.] in your breasts, – a guidance and a mercy [explaining lawful and unlawful things, etc.] for the believers. [10:57] [Ref 1:]
The Correct Manner In Which We Should Approach The Contemporary Sciences
Imaam Abdul Azeez Bin Baaz [rahimahullaah] said: Indeed, that which is stated by the astronomers about the celestial bodies, their sizes and the distance between them, and that which is said about the earth [i.e. by the geologists etc] is categorized into three affairs: [a] That which is backed by the sound knowledge-based proofs [i.e. the Sharee’ah], therefore it is accepted. [b] That which the knowledge-based proofs [i.e. the sharee’ah] declares to be false, therefore it is rejected. [c] That which there is no proof to either accept or reject it, therefore it is unproven until a person from the people of knowledge [i.e. upright scholars of Ahlus Sunnah] examines it [i.e. examines what it indicates based on the Book and Sunnah] to show whether it should be accepted or rejected. As for accepting it without [sound] investigation and observation, but merely accepting it by blindly following them [i.e. the astronomers, geologists etc], then this is impermissible because of the numerous mistakes that occur as a result of that, and speaking -without knowledge – about Allaah and that which He has created [i.e. the entire universe and all that is within it]. [Ref 2]
Shaikh Saaleh Aala Ash-Shaikh [hafidhahullaah] said:
Studying the prophet’s biography (sallallāhu alaihi wa salam) and reading it, makes the certainty of the believer to become stronger, makes his steadfastness and perseverance upon the religion of Allah stronger, makes the believer’s heart to be honourable due to Islam, ennobled by [his adherence to sound] Islamic monotheism, ennobled due to what his heart contains of knowledge and awareness of Allah, ennobled due to his belief in Muhammad (sallallāhu alaihi wa salam) and ennobled by that which Allāh sent down upon his Messengers.
وَلِلَّهِ الْعِزَّةُ وَلِرَسُولِهِ وَلِلْمُؤْمِنِينَ
But honour, power and glory belong to Allah, His Messenger (Muhammad sallallāhu alaihi wa salam), and to the believers
These are from the many benefits that every believer benefit from by studying the biography of The Chosen One (المصطفى) (sallallāhu alaihi wa salam). 
Shaikh Abdur Razzaaq Al-Badr [hafidhahullaah] said: Indeed, one of the greatest bestowals on a believing slave of Allaah – which leads to guidance and righteous deeds -is that Allaah [The Mighty and Majestic] facilitates for him the path to seeking knowledge, grants him an ardent zeal and eagerness for knowledge. Seeking knowledge is something one never feels that he has acquired enough, rather whenever a path to knowledge is made available, he pursues it.
Allaah protects the student of knowledge, guides and aids him, therefore it is obligated on a student of knowledge to exalt the affair of turning to Allaah [in submission, obedience etc] and that what he learns should be a proof for him and not against him; and that Allaah increases him in knowledge, facilitates him with the path to good and guidance. “Whoever follows a path in search of knowledge Allaah will make easy for a him a path to paradise”.
One of the noblest aspects of knowledge – an affair that occupies a mighty station- is to pay close attention to the characteristics of the Prophet, his specific qualities and deeds by way of which Allaah distinguished him from everyone amongst mankind, his manners, etiquettes and biography. That is because he is the greatest Imaam [leader] and the perfect example. Indeed, Allaah [The Mighty and Majestic] commanded us to follow his example, made him an Imaam [leader] and example for us. Allaah [The Mighty and Majestic] said:
لَّقَدۡ كَانَ لَكُمۡ فِى رَسُولِ ٱللَّهِ أُسۡوَةٌ حَسَنَةٌ۬ لِّمَن كَانَ يَرۡجُواْ ٱللَّهَ وَٱلۡيَوۡمَ ٱلۡأَخِرَ وَذَكَرَ ٱللَّهَ كَثِيرً۬ا
Indeed in the Messenger of Allah (Muhammad) you have a good example to follow for him who hopes in (the Meeting with) Allah and the Last Day and remembers Allah much. [Surah Al-Ahzaab. Aayah 21]
This noble Aayah – as the people of knowledge have stated – is a basis to established the fact that the Prophet [sallal laahu alayhi wasallam] is to be emulated; [but] emulating him cannot be actualized except by way of acquainting oneself with his characteristics, his qualities in general, his specific qualities and deeds by way of which Allaah distinguished him from everyone amongst humankind, his manners and etiquettes. The one who is unacquainted with the Prophet’s [sallal laahu alayhi wasallam] characteristics and manners will not be able to emulate him, and that is why the scholars [of Islaam] have written beneficial books regarding his characteristics and qualities.
The manners and qualities of the Prophet [sallal laahu alayhi wasallam] are a means of inviting [mankind] to this mighty religion [of Islaam]. Indeed, many people- during his era and thereafter – have been guided through their acquaintance with his manners and qualities. One used to come to him whilst harbouring the severest hatred towards him, but after meeting him and [observing] his great [unmatched noble] etiquettes, noble manners, lofty dealings and benevolence, the person would depart whilst loving him more than everyone else on the face of the earth. Therefore, his characteristics are a means to calling to this religion- a weapon for the one inviting the people in the path of Allaah.
Speaking about his qualities, emulating him and calling others to emulate him strengthens the religion of Islaam, because he was the one whom Allaah appointed to convey and explain the religion to humankind. Allaah chose him and he is the best of all the slaves of Allaah- the greatest in his servitude to Allaah. Calling the people to emulate his qualities is a means to calling people to believe in the religion ordained by Allaah and a means to strengthening the belief of the one who has already believed in his Messenger-ship. This is why turning away from his Seerah has been the cause of people’s inclination towards the path of losers amongst men and women [i.e. those upon a path other than the path of Allaah]. As for the biographies of the Imaams of Guidance- the greatest of them being the Messenger, they are a means of rectifying the person and a means to safety from corruption and evil. On the other hand, the biography of the losers is a path that will lead to evil, ruin and corruption. Allaah [The Mighty and Majestic] said:
قَدۡ كَانَتۡ ءَايَـٰتِى تُتۡلَىٰ عَلَيۡكُمۡ فَكُنتُمۡ عَلَىٰٓ أَعۡقَـٰبِكُمۡ تَنكِصُونَ
مُسۡتَكۡبِرِينَ بِهِۦ سَـٰمِرً۬ا تَهۡجُرُونَ
أَفَلَمْ يَدَّبَّرُوا الْقَوْلَ أَمْ جَاءَهُم مَّا لَمْ يَأْتِ آبَاءَهُمُ الْأَوَّلِينَ
أَمْ لَمْ يَعْرِفُوا رَسُولَهُمْ فَهُمْ لَهُ مُنكِرُونَ
Indeed My Verses used to be recited to you, but you used to turn back on your heels [denying them, and with hatred to listen to them]. In pride [they Quraish pagans and polytheists of Makkah used to feel proud that they are the dwellers of Makkah sanctuary Haram], talking evil about it [the Qur’an] by night. Have they not pondered over the Word [of Allaah, i.e. what is sent down to the Prophet], or has there come to them what had not come to their fathers of old? Or is it that they did not recognize their Messenger [Muhammad] so they deny him? [i.e. this is a rebuke against them because all of them – young and old – knew his lineage, truthfulness and trustworthiness, yet they turned away from his message]. [Surah Al-Muminoon. Aayaat 66-69]
This shows that contemplating on the Qur’aan and acquainting oneself with the Messenger’s guidance and biography is a path leading to safety, and a safeguard against turning back on one’s heels [i.e. a safeguard against turning away from the guidance he was sent with]. On the other hand, abandoning the Seerah of the Prophet and inclining towards the Seerah of the losers [i.e. those men and women upon other than the guidance of the Messenger] will lead to ruin. The people became corrupted – in this era – after being put to trial through movies and films; but had they turned to the biographies of the Prophets and the noble companions of the Prophet Muhammad, they would have found guidance and a path leading to steadfastness. 
[Ref 1: An Excerpt from I’laam Al-Muwaqqi’een 4/375-377- slightly paraphrased]
[Ref 2: An Excerpts from ‘Al-Adillah An-Naqliyyah Wal-Hissiyyah Alaa Imkaanis Su’ood Ilal Kawaakib Wa Alaa Jarayaan Ash-Shams Wal-Qamar Wa Sukoon Al-Ard’ page 74. slightly paraphrased]
[3: Silsilatu al-Muhādarāt al-‘ilmiyyah Vol.4 Pgs. 506-507]
[4: Source: An Excerpt from: [شرح المختصر في صفات النبي ﷺ وأخلاقه] Lesson 1. slightly paraphrased]