Hi Ken,
You'll be able to find out what work your Audi has had done at the main dealer by giving them a call :)
Audi Jeep the records of all work carried out on their vehicles. Also I believe the cambelt should have a date on it but don't quote me on that.
I know it's the expensive option but if it were me I'd be doing a cambelt and water pump change as well as a full service just to be on the safe side :) plus doing a full service will.pribabky give you a good indication of when it was last serviced by the condition of the oil, air filter and oil filter.
These engines are tough. My a6 has the sister engine (2.5tdi) which has coved 328,200 miles and the engine and gearbox are the original and have never been rebuilt.
Hope IV helped :)
Cheers
Steve