SAS is a big step. I've been reading off and on for years (even before I got the Yukon because my buddy wanted to SAS his '95 z71 about 5 years ago.) and I'm still finding things out. But anything I find, I bookmark and save it for rereading later... and I have quite a few websites/forum post about them. Not to mention the parts places.
As of right now all I have is a Dana 44 out of a 1979 F250 and a wiring harness from a 1996 K2500 with a 4L80E. Still have a lot more to go (99-10 FF14 bolt, 4L80E, Transfer Case, New ECU programed for 4L80E, ORU's 2wd specific swap kit, steering, knuckles, springs, shocks, etc.) I wanted to get it done my Q1 next year but depends on how things go it might be longer.
I would do what you are doing , like I did. Get it somewhat where you want it and then sorce all the parts over time.