Also, take a look at the brownell's website. I think under their guntech link.
There is a complete series of videos (2-3 minuters per) of one of their guys doing a complete (and I mean complete) assembly, including fixed buttstock and adjustable, standard handguards and freefloating.
They start with some background on the variants (A1, A2, A3, etc).
It doesn't cost anything to watch them online and you can print out the text as instructions.
I did and have my complete lower ready for an upper. I didn't want to build the upper so I'll buy that complete.
AR's and AK's are very easy to assemble if you have the proper tools, a good TM and the patience to follow instructions..I build a AK in about 1 1/2 hour now, not including demilling...A AR in about the same if from scratch...enjoy the results and have fun....
AR's are a very basic, straight forward rifle. Do your homework, assemble it on a workbench with good light and a good manual. If you are just doing the lower, its a cinch. The pivot pin can be a challenge without the proper tool, but it can be done.
The upper gets tricky. Just take your time. If you dont feel confident about the headspace, invest a few bucks and buy gauges to check it. Its not rocket science.