iwire is decent but charges like 1k to do a merged harness. thats crazy to pay that when shops can do it for 700 or less.
as far as swap goes i've heard its really simple. either get an entire wrx and swap over the dash and everything and merge in little stuff like doors and windows and lights. or get an engine, harness, ecu, and notched cross member from a wrx and have it merged. I've been told its a weekend swap so can't be that hard once you aquire all the parts.