Jaden, Logan23 and VP have an excellent primer for projects of this size. (Granted this was intended for Tc's but I think this project is so big that it applies as well...particularly the last part)
Also, notice that none of the posts made in this thread have been designed to rip on you*, consider them as advice to build your skills up before tackling something so difficult. It's like trying to construct a house after reading just 1 book (or tutorials), sure you can give it a shot but I would rather start by learning how to build a birdhouse first, then work up to the real house...believe me, I've made that mistake before. Learn and appreciate how much time you'll need to spend on this before taking the plunge.
Also keep in mind that even if you were shipped all the files that they've worked on, it still wouldn't encompass all of the ideas they've had that simply haven't been possible due to the engine or other problems...you'd be starting blind.
*Ok except for miss sara's