I am not a Muslim but I have been reading alot about Islam recently. I have many questions and hope those on this board may help me in answering them over the coming months.

What I want to ask now is do Muslims have to follow the Sunnah and Hadith? My reason for asking is that as far as I am aware (correct me if i am wrong) many traditions which are followed by Muslims do in fact come from these rather than the Koran. The one that springs to mind is the rule that a Muslim woman cannot marry a Jewish or Christian this not being in the Koran itself. However in the Koran God said "we have not neglected anything in this book" [6:38] From the way I am reading it God himself is saying nothing other than the Koran is necissary. So why are Hadith and Sunnah followed so closely and is claiming that it is necessary that they are followed going against the word of God as I quoted above?

Assalamoalikum Quirk
As Muslims, we believe in the Quran and the Sunnah. So yes. But let us define what Sunnah/Hadith means. It is anything said or done by the prophet Muhammad pbuh or infront of him which he allowed. You see as Muslims, we believe that human beings require guidance in various aspects of life. Quran is that guidance to us. But it's like when a teacher explains a topic, he gives an example. Without an example, it is difficult to understand a topic, may be even impossible. So when God explained us, our purpose, our dos and don'ts, He also gave us an example to follow. That example is Muhammad pbuh. We require this example because it makes life easier. Quran explains commandmants and Hadith/Sunnah explains Muhammad pbuh, his life etc. As Quran says:
"Verily, in the prophet of God, there is the best example (to follow) for you "
Hadith is also what prophet Muhammad pbuh ordered to do. And Quran tells us in numerous places:-
"Obey Allah and obey the Messanger (pbuh)"
So you see, Hadith/Sunnah is important
Moreover, Hadith/Sunnah explain the Quran. They can also be called the commentry of the Quran. For example, Quran stresses upon praying but does not tell us how to pray. We know how to pray through Hadith
I completely agree that God has not neglected anything from Quran. Quran is the complete guidance. But you do require someone to explain the Quran to you. To give you an example, suppose I hand you this Quran in arabic without a translation/explanation and you suppose do not know arabic, you won't be able to understand Quran at all. You would require a translation/explanation of Quran. But you cannot object that why do I require something extra i.e translation/explanation when Quran says that it is complete guidance. That would be illogical. Similarly, One requires an explanation of Quran in the shape of an example who has spent his life precisely according to the Quranic principles. Don't you think Quran, the guidance given by Allah would be more understandable, clear or comprehensible if we are given a perfect example? Alhamdulillah we have been given this example. He is prophet Muhammad pbuh. I hope I helped.
May God guide you and me to the right path.
Ali

This discussion can be very long and it can not be explained into small posts in forums, however if you keep your questions on specific topics than it is easy and possible to answer them. As for what yoy have mentioned that from what you understand from the Qur'an is that God says that nothing other than the Qur'an is what is necessary, this is incorrect as the Qur'an itself makes obligatory the sunnah:

"... So take what the Apostle gives you and stay away from what he forbideth you. And fear Allah; for Allah is strict in Punishment" (59:7)

We are ordered to follow everything that the Messenger gives us because:

"And he does not speak from his own desire. It is no less than a revelation revealed to him" (53:3-4)

And this includes everything as:

"And they ask you no question but We reveal to you the truth, and the best explanation for it" (25:33)

"But no by thy Lord they can have no (real) Faith until they make thee judge in all disputes between them and find in their souls no resistance against thy decisions but accept them with the fullest conviction" (4:65)

Look carefully may God guide you to the truth, how in the last verse(4:65), the condition for belief is defined by making the Messenger the judge in all the disputes. It does not mention taking the Qur'an as the judge but taking the Messenger as the judge in all the disputes. This not because the Qur'an is not the prime sorce but because "he speaks not of his own desire, it is nothing but a revelation that is revealed to him".

As for the prohibition of a muslim woman getting married to a jew or a christian or any other person of polyteistic beliefs it is in the Qur'an.

"Do not marry unbelieving women (idolaters) until they believe; a slave woman who believes is better than an unbelieving woman even though she allure you. Nor marry (your girls) to unbelievers until they believe: a man slave who believes is better than un unbeliever even though he allure you. Unbelievers do (but) beckon you to the fire. But Allah beckons by His grace to the Garden (of Bliss) and forgiveness and makes His Signs clear to mankind: that they may celebrate His praise" (2:221)

This is enough God willing for this matter.