Welcome to the forum !!!
In my opinion its not a bad price but if the transmission is gone expect some big costs replacing it.
The auto boxes are known to be troublesome on the Audi so manual is best really.
Mileage wise everything else should be fine engine,turbo etc as long as car has full service record oil changes etc.
suspension rattle may just be rubber bush/track contol arm perished..
im guessing its a B5 model 1996-2000 ??
I would say go for it at that price should last you well up to 200k miles once small things repaired..
