theres a post in the maint section by RM telling you how to do it. Its simple.
I have most the parts if you need any as i got half way through doing it before i got the GTI.
It will be highly unlikely that your car is geared up for it by having the loom or the fusebox connections.
I have..door cards, handles + switches, door wiring looms for both front doors, the dash wiring loom with thermal fuse, the electric mirros (without backs) as you might aswell change them aswell as they are in the same circuit, i have the motors and regulators to but i think im going to hold on to them!