Excellent choice for a car to buy Ben,
I bought a 1992(in 1995) with 75K and sold it at 208K(1998)
The only thing I replaced in all those miles was the glow plug regulator(700 at the MB dealer) and a vacuum pump (250.00)...other than that(maintenance items) tires,timing chain,glow plugs ... an excellent car....in fact I would say the 1990-93 300D 2.5 is probably the best compromise between the old and new diesels....all the acceleration,smoothness of the new and the low upkeep dollars of the old.
I think the crucial thing is that the car was taken care of....I always look for one owner,one MB dealer sold and serviced cars....I may pay a little extra but I think it has served me well in regard to obtaining quality cars.
1992 300SD 111K