Honestly, there's really there is nothing to it, as long as you can get a complete rear clip. Since you are going from N/A to turbo, you would want the entire rear half anyways (everything in the engine compartment, tranny, exhaust, sensors, wiring harness(s), ECU, ect...). Getting this will save you so much time and effort, but will cost you alittle more than say, red necking your way around converting a turbo engine to run on some of your stock components. Buying the clip will make it as simple as remove and replace. Just be sure you get one from a reputable place. And if you are going to install it yourself, be sure to take you time, label every nut and bolt... buy the turbo BGBs (even though they are horrible books).
with a cut harness.. prepare to trace every line, by the end of that swap, you will have intricate knowledge of the car's wiring schematics... also be prepared for not being able to drive the car for a long time if you've never done wiring like this before.
im sure that will help immensely, however you will still have to study the intricate wriing diagrams, and this will prolong the swap time significantly. There is a LOT more that can go wrong w/ the added step of wiring...
Since the Gen3 swap has gotten so popular over the last few years, there are actually alot of shops that could help you out on this, if you choose to go the splicing route. I believe there was even a guy making converted harnesses using the US harness as a base for the Gen3 swap over. Have you tried posting Q's in the Hybrid section? If anything, someone there could probably point you in a better direction, or at least drop a reliable name for more info.
According to mr2biker91, all you have to do is match the wiring from the cut harness to the fuse panel. He said that there are like five or six wires that don't get hooked up, but his car runs perfectly fine. As far as the rest of the swap goes, it's straight forward. Drop the rear end of the clip and swap it in, then splice the same colored wires = done.