I've done it. Minimal wiring. You just need a ton of parts. You have to get dirty and lift heavy stuff, too.

I'd go to a u-pull-it style salvage yard to make sure you get everything. Basically everything between the differential and the block has to be changed.

There are plenty of corners that can be cut as well (used parts instead of new). I'd suggest getting a new Exedy clutch ($99 on eBay), and clutch master/slave/hose ($35/$25/$10). That leaves tranny w/bolts, driveshaft, shifter (w/boots and knob), flywheel w/bolts (resurfaced, of course), clutch hard line, clutch pedal, and most importantly starter bolts. That later are easily forgotten, and hard to find.

For wiring, just jumper the starter interlock. You might also want to connect the reverse switch and the speed sensor output. Download a FSM from zeroyon.com to figure that one out.

If you actually go through with this, I'd be happy to lend further technical assistance. It will only cost you a test drive in your GTI. I'm thinking about buying one.