Opinions Needed Before I Buy Car

I was just given the chance to pick up a 1985 190D diesel. The body is excellent except for some rust on the passenger door. Interior is super clean and everything works. The car has 230,000 KM or about 138,000 original miles. How good was the engine in this car? Anything that they are notorious for? How was the general reliability of this model? The guy wants $4000 US for it. I am looking at it for my wife to replace her 1994 Jetta Diesel. Are the 190D known for expensive repairs like the newer Mercedes with their $1500 wiring harnesses? Any and all advice would be appreciated. The guy will hold the car for until Monday for a decision. Are these diesels aluminum block? Should tensioner and/or chain be replaced at this mileage? Buy - or Pass - Please help!