The low beams and high beams are both H7 bulbs. The fog lights are H3's.
Yes you can my friend had them on his golf mark 4
its only on European models, to make it work you need the euro switch and the appropriate wiring
mk 4
Pentosin G12
4
on the right side of the stearing collom. I own a 1973 Mark 4
The horn is located under the front bumper behind the fog lights. Slide your fingers up under the and remove the 2 clips attaching them then replace it.
Mark 4 (or IV). It's the version that was manufactured between 1999 and 2005 for the Golf and Jetta.
you can tell by the front headlights if they are a long flat lights its a mk 4 and if not the its a mk5
Pull it off
You can find a nice D.I.Y. with pictures here: http://laudeman.com/volkswagen/golf_headlight.html
it is a device that is inline of the speedo to give the speed of the vehicle its normally on the gearbox.