Don,
I am not sure on rebuilding the original pump but replacement costs
sounds kinda high for a rebuilt pump. I did mine about a year ago and
ordered it mail order thru European Precision in TX, USA for about $200
and change + $50 refundable core charge. I am sure there are others
out there. The swap-out was easy accept a little messy. Good luck on
the project.
Regards
Mark
'82 Audi 5K-S