Is the Qur'an contradictory? (I doubt it)

Dear Islamicity forum members,

My question is directed to those members with a deep understanding of the Qur'an. The only holy book I'm currently familiar with is the Bible as I was brought up as a Christian, so please excuse me if I display ignorance in my search for knowledge.

My main contention is as follows: the Qur'an does not contradict itself. That is to say, it may be possible to quote or misquote sections of the Qur'an out of context to give the appearance of internal inconsistency or contradiction, when in fact a full reading shows this not to be the case.

The particular apparent contradiction I'm referring to, brought to my attention by non-Muslims, is the idea that the Qur'an states the following:

That the Bible is a previous revelation of Allah, and that it is true.

However, if the Bible is 'true', the Qur'an cannot be, since it contradicts the Bible. Therefore I am of the opinion, unfortunately uninformed by actually having read the Qur'an, that this is a misrepresentation. I've been directed towards the following references as supporting this likely erroneous idea:

Surah 6:114 "...Those unto whom We gave the Scripture [the Taurat (Torah) and the Injeel (Gospel)] know that it is revealed from your Lord in truth..."
Surah 6:34 "And none can alter the words of Allah"
Surah 6:115 "And the Word of your Lord has been fulfilled in truth and in justice. None can change His Words. And He is the All-Hearer, the All-Knower."

I'd like to thank you for reading this far and I'd be very grateful for any assistance you may be able to offer. Just to reiterate, this viewpoint, that the Qur'an is self-refuting, is not one I personally hold. I actually find the idea ridiculous, I'd simply like to learn the most efficient way to debunk this premise.