See cashflyer's thread:
http://forums.pelicanparts.com/off-topic-discussions/841049-ar-spoon-builders-any-help.html
Sadly it isn't trivial these days because several of the components have gone out of style. Hell, 20" uppers are like hens' teeth.
After shooting your $450 rifle the first thing you will want to do is upgrade the FCG (fire control group - trigger/hammer). I strongly recommend the Rock River Arms 2-stage National Match trigger. Best $100 you can spend on an AR-15. IMHO.