I'd get a ppi before I made an offer.
It doesn't bother me that the car has a problem. It is 30 years old, and there will probably be several things to look after.
I'd just want to know what it is going into and what it's going to cost to fix it, and use this against they guy to get him to lower the price.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".