Arfcom build thread:
AR15.COM :: Forums :: Assemble your own LOWER, UPPER, FREE FLOAT, TRIGGER, GAS BLOCK - Step by step instructions!
Has all you need to assembly, should be plenty for ya! For all their complexity, AR's are pretty damn easy to work on.
From what i know, the only real difference is that Colts use larger trigger group pins than the other manufacturers... that and they charge a premium.
