i had one for sale a while ago. i picked it up for $180 CDN, including the SI harness, throttle body, ecu, resistor box, fuel rail and injectors. when someone wrote my car off, i pulled that out and sold it for $150 without the harness. if you can find one at a wrecker's and they arent going to core the engine, then you are lucky. dont offer them any more than what i told you.
easier to find this upgrade on forums. it took me about a month of searching to find someone who wasnt a pirate, and who could tell me details about the car it was coming out of (like mileage)
the wiring itself isnt so bad either. there are a few good write-ups around. i will post the links later today when im back at home.