It would be fairly easy to do if you had the correct pinouts, I am a controls electrician, I fabricate electrical panels for machinery and I did my little brothers harness, it was probably the hardest thing I have ever wired, but we were going from a usdm to a jdmrc motor. It was easy to find the us wiring diagrams, but getting everything for the jdm harness was tough, I had to goin gt4oc.com to get all of the diagrams I needed, but once you have those, document everything (label) from each harness and take measurments from your stock harness, off of reference points like were there is a "Y" in the harness. That way everything will go back to the way it was, and if you want that cool wire loom those companies use you can get it at grainger or sonicelectronix.com or any place like that and it is fairly cheap. All I can say is document, document, document, and only solder or run completely new wires all the way to the ecu if you can.