89 Vortec SWAP

Hey My tranni I believe is gone, my 89 blazer won't go in reverse and the transfer case only shows Nuetral. Anyone have any ideas of what else it might be? I am pretty sure it is the Tranni though. Anyway I found a 95 Jimmy that had been rolled with a perfectly fine engine, tranni and transfer case with only 66,000 on it for 600 bucks. I was wondering how hard that swap would actually be. I have never worked with computers at all except a direct engine swap with a little jeep 4 cylinder. Is it a real pain or what? Where is the comp in the 89's and 95's anyway? thanks!