1999 Audi A6

Yes.

Timing belts should be changes on a mileage interval which you are near with your V6

OR ...

based on a duration of four or five years maximum. You have significantly passed that point and are driving on borrowed time. The risk - you loose your engine abruptly and the car dies in traffic. Repair costs will probably run more than you car is currently worth.

Having the job done at an Audi dealer will probably run $1,200 to $1,600.

You might save some money going to an independent Audi mechanic. Do NOT take it to any mechanic. Be sure to check with other local Audi owners to find the name of a reputable Audi mechanic. An independent might cost under $1,000.

The job requires changing a number of parts other than the timing belt itself. The failure can also be caused by a failed water pump or belt tensioner pulley. As long as they are taking it appart it is strongly recommended to replace the thermostat and a few assorted seals. It will also require replacing the engine coolant which must be the recommended Audi coolant.

It is not cheap but a lot less than the alternative.

I have a 99 A6Q. Service for the timing belt, tensioner and water pump is recommended at 70K intervals. As the previous responder indicated, it won't be cheap. Throw in service on ball joints, cv ends and boots, plus other sundry susprnsion parts plus the regular maintenance intervals and over a short period of time, this car will, in maintenace costs alone, be your second most traumatic hit to your wallet behind maintaining your house (if you own one). Hopefully you chose this car because of it's handling, styling, and general feel. These are the only reasons one would (as I have) invest so much into a depreciating asset.

Do it! Also get the tensioner and water pump replaced as these are problematic on this model.