Treelander- this is what I would get:
BFH-3 or 4 lb, for knocking out those da-n barrel pins.
Plinkers rivit jig is a good tool, but I would get a 36" long handle bolt cutter and mod the jaws for pressing the rivits. works just as good and much faster, and a lot cheaper. Gunco has articles on these.
A 12 or 20 ton press is nice for popping the barrel out of the trunnion, and for pressing sights and gas blocks and such off the barrel.
1/4" or 3/16" allthread rod for pulling the barrel back in to the trunnion. Gunco has howto's on this.
The best brand of hardened punches you can buy. no cheapo chinese or indian made crap.
a triggerguard rivit jig.
If you want to bend your own receivers, you'll need a receiver jig for that. Make sure that the jig you buy comes with the top rail bending jig also.
a cheap HF tig welder
a 5-6 hp air compressor and assortment of air tools
airbrush, for painting your guns
As to your question about headspace, that's set by the depth of the barrel in the trunnion, and held in place by the barrel pin. If headspace is off, the barrel needs to be pulled, the pin groove in the barrel welded up, the barrel turned in the lathe, then reinstall the barrel in trunnion and slowly squeeze the barrel in, while checking HS, when HS is correct, redrill the barrel pin hole, then reinstall the barrel pin. This is best done by a professional AK smith.