ocd_2k3

I had a jdm engine swapped into my car because i blew my motor. I took it to a mechanic, and he did not know what he was doing, and he ended up messing up. He put the jdm wiring harness with a usdm ecu which is stupid. So know i have to swap the entire wiring harness. What is a reasonable price for doing this, or is it possible for me to do it with a couple of my friends?

Any replies or info will be greatly appreciated