Why on earth are you taking advice on your car when you haven't given people any information about the car in the first place?!?
I can see you gave some details further down, but that's really a "how long is a piece of string question" without that info.
Any TDI + auto box is a tougher remap as the TDI remaps usually focus on unleashing a LOT more torque at the lower revs that manufacturers normally tune out specifically to protect components.
If you remap a manual TDI and then drive it carefully (mostly just get the clutch ALL the way out before giving it the beans), then you can protect the clutch and put another 100k on the car without a problem.
If it is a torque converter auto and you drive the car aggressively, then it will put a lot more strain on the clutch.
If it is a DSG, then you're in slightly unexplored territory as they're not known for their torque prowess, but the modern DSG's are beign put in everything up to the 300lb/ft+ TDI's (just not the BiTDI / V8 TDI's).
If it is a CVT auto (multitronic), then it will usually do the gearbox a lot of damage fairly quickly.
Audi have never put a multitronic in a quattro and I think the TDI spec DSG's are too new to have been put in a C6 A6, so yours is probably the torque converter....
I'm not going to answer your question as it is a risky one with any auto... but if you were going to, stick to a repuable company, that does the remap specifically for your engine + gearbox combo and only as a hot-swappable module, so you don't lose the warranty as there's a decent chance you'll need it.