I found the book The AR-15 Complete Assembly Guide
by Kuleck & McKee to be a great resource. There is a series of AR-15 assembly videos
on Brownells web site that are very good as well. I believe they sell these on a DVD, but it's just as easy to watch them on the web IMO.
Beyond that, be prepared to spend a lot of time looking for components, especially if you want to get reasonable prices. Some things are still very hard to find nowadays, and prices are still pretty crazy. Lowers and lower parts kits seem a little easier to come by than they were a few months back, but barrels, bolts and BCGs are still scarce.
Search through some past topics here on FT - a lot of good advice has been passed down.
Good luck. Let us know if you have some specific questions.