When my old (now out of business) company had the Delphi contract to repair VW's radios, all radio's had to go through the dealerships to be fixed. The dealers did radio repairs on exchange basis only. I don't know who has the Delphi contract now, but the belt was only $7.00 at most when we had the parts.
Crutchfield has a lot of options for aftermarket radios for VW's, I was looking at this one
JVC KD-HDR20 CD receiver at Crutchfield.com to replace my OEM radio.