I built my FAL years ago and it wasn't a huge ordeal except for the locking shoulder, which thankfully my buddy had a bin full of. I'm putting together the tools/parts for a couple of AK builds now.
My press was backordered for several months and finally arrived a few weeks ago. I got my excellent condition Romanian parts kits from DPH Arms, and they came with the G2 FCG for $125. The bores are minty, and they'll likely not need refinishing.
Receivers from Global Trades are backordered 6 weeks last I checked. Since I don't have a spot welder or the desire to buy one, I'm getting their (I think) type 3 receivers which already have the rails and trigger guard installed. I plan to do rivet builds (have parts for 2 builds). Some guys over on ak-47.net sell rivet jigs, but they're more than I care to pay for so I'll be manufacturing the rivet crusher from bolt cutters. I foresee this as being the most difficult part, because it's a lot of freehand work with a dremel.
Headspacing is easy, because if you keep the same barrel/trunion/barrel pin together, the headspace won't change. The rear trunnion takes a lot of time and patience with a drill press and cutting oil.
I've seen several good build guides on gunsnet.net forums and a few other places. They're bookmarked on my other computer, I'll try to remember to post links when I get home.
I'll be posting a complete guide with pics and maybe videos as my build progresses, but since I haven't placed my receiver order yet it's still some months off.