hello, i am about to buy a 1998 A6 2.8, it is in great condition and very clean all around. it has 138,000 miles on it right now. the current owner said the timing belt was done at 115,000. before i buy this car i was just wondering is there anything that i should really keep my eyes out for? he is going to sell it to me for 3900$, dose that sound about right, and if taken well car of how many miles should this car go without a major engine problem?

Thanks