The wiring is not a big deal at all as far as the engine and trans is concerned if your willing to pay someone to build you a harness. I tried to save money by using a company who was cheaper then speartech but in the end they couldn't get me setup with working computers. So I got my harness built from one place and my computers from speartech. If you are willing to pay the $1500 that speartech charges it is really a plug and play operation to wire up the engine and trans. As for wiring the rest of the car I am actually doing that myself right now and am building the harness for myself.
http://speartech.com/