CSchmidt - yup!
Same thing I did. Hope I banged that rivet solidly enough. No need to take the window out - in the later manual it tells you just to loosen the track, and keep the window wedged in the up position. It worked for me.
Regreased the armature ("regulator") teeth while I had it out...
You need to take that armature out out for two reasons - to drill out the old rivet, and to bang in the new one.
Used the marks on the paint to reallign the bolts and screws when I reinstalled, and the window now works and has exactly the same play as the one on the passanger side...
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)