Someone linked this video series that Brownells did and I found it incredibly educating. And it was effing cool too. My first build I put together a stripped lower and bought a complete upper. My second build might be a custom upper too, we'll see. Check it out, even if you don't use it for a reference, it'll show you the general process. They also have purchasing checklists and the lists of tools you need (some may be extraneous, but it'll give you an idea).

http://www.brownells.com/.aspx/lid=11004/learn/

Good luck. I agree with everyone else, it's all about having fun. Be safe.