check out
www.ncix.com
You can order all the parts and build your own, or select the part out, and for $50, have them build it for you and test it as well, then ship it out. Great prices, and its a Canadian store to boot!
I recently built my own computer, and I don't recommend just jumping into it, especially when dealing with a rig that expensive. I'd trying buying a $50 jalopy from somone's closet, and then just take it apart, clean it, put it back together again, and see if it still works. Anyway, check that site out, its great! And it price matches as well. Good luck!