I'm using a 02 PCM with my 03 engine so there is some interchangeability. Check the Painless Wiring web site for their compatibility chart, it'll give you a good idea of the differences through the model years, although (and you'll hear this a lot) it's easier for simplicity to get everything with the engine. You can not use your 90 computer with the new engine.

You also asked whether the stock wiring will be good. If you are referring to the engine harness, no, your 90 harness will not work with the new engine. You'll need to either modify a stock Gen III harness to interface with your trucks wiring or you could purchase a new swap harness form one of the many vendors (Nelson, site sponsor makes these)

Please read all the swap threads in this forum and the part number sticky to get an idea of what else you need, then ask for help with any specific questions that remain unanswered.