I agree with Tyson. Speartech wiring harness and a GM ECU. HPTuners or EFILive (I use that one) to modify the GM tune in the ECU. In my opinion since this is your first attempt at EFI would be to wire the car with a Speartech harness and grab an ECU out of a post 2002 F body. Oh scratch that last sentence since I don't know what year engine you have. In any event, get her running and then get yourself used to using the tuning software. Once you do that and you are happy with the way the car runs, then you can start with one modification at a time. Tuning as you go along. Believe me, this is the only way to go without paying someone else to do the tuning for you.
So, what year motor did you get?
Joe