if you swap it would it be done by yourself or a reputable shop?
if it's a reputable shop you shouldn't have to worry about the mechanical and electrical aspects of the swap at all. my car was swapped 10k miles ago in Nov. of 2007 and so far all the hiccups i've had are very minor, and all due to bad luck buying bad used parts.
unless you're planning on getting a very old JDM engine, for me i opted for an 05 USDM engine for complete legality and reliability. to me swapping my 2000 RS by Garage Tuning with 05 engine/tranny = buying a used 05 STi in terms of risk, except my insurance is way less and my car is 350lbs lighter.
not sure what your budget is, but it's important to do it right the first time when it comes to swapping. if you try to find the cheap way out most of the time it'll bite you right back in the ass in the near future. just my experience...
FWIW i much prefer the driving feel of the GC with the same engine/tranny over the newer chassis, it just feels much more raw and i also don't like heavy cars...the EVo/STi at 32xx lbs + curb weight is too heavy for me, and you can esp. feel all that weight when you're rolling off at a green light or in quick transition corners. the downside of the weight saving for the GC is chassis rigidity, but i personally consider it a worthy trade off.
good luck mate.