Yeah you just need to get the H7 ones if you own a GTI. Powerbulbs has a pretty straight forward way of making sure you get the right ones. You just enter in your car details and it tells you which bulbs you need to get for which light.
The main beams are easy to replace by just twisting off the old set and popping in the new ones. The high beams are a little harder as they are held in place by a wire cage, but still not that hard to do. As for the sidelights, some people on here complain about how hard they are to replace, as they have hurt their fingers trying to pull out the sidelight housing, but I found it dead easy. I just used a set of vice grips and to pull out the housing and then pushed it back in with my hand, easy as pie.
There is a thread under the Mark V section somewhere with pictures and stuff, no idea where though?
One thing I did do though after replacing the lights was get the alignment checked, but my car was going in for DSG oil change anyway so it wasn’t too much hassle to get the stealers to do that at the same time. The brilliant thing was the stealer I brought the car from paid for all the work I had done which is nice.