Well rule number one is don't buy a car thats going to take alot of work to fix it and rule number 2 always go to a specialist for parts not the manufacturer otherwise it's going to be fucking expensive.
and that applies to everything, hopefully with the popularity of Ashes To Ashes the market for making replacement parts for the ur quattro will bloom and more places will start to stock parts for them or create'em like the 60's and 70's muscle cars of now.
For me the ur quattro is pretty much everything I'm looking for: 4 seats, good trunkspace, good visibilty, handles, stops, is well built, reliabile, fast and not too conspicuous in a dark color.
I mean if you dont know what it is you wouldn't bat an eye at it, unless the turbo kicked in right next to you
FYI personally I'm not really an audi guy save for this one car.