Mercs from that era are great cars indeed. Regular basic servicing and keep an eye out for tinworm, and it will outlast you.
My 190D is almost 27 years old, has done 227000 miles and still drives great, although I did have to chop some serious rust out of it yesterday.
And yes, Merc prices aren't as exhorbitant as urban myth often suggests.
I thought they were very good against rust? Certainly way better than the Mercedes after them and also the Omega?
I think the whole shell is fully galvanized, no?
They aren't particularily bad for rust, but a car of that age will rust over time. 190,s have known rust spots (jacking points mainly) just like most other cars, but most other cars don't make it to 26 years old.
Havent heard of galvanised Merc shells. My 1990 Merc certainly doesn't seem to have one.
Later Mercs approx. 98 - 03 were appalling for rust. Five year old examples could easily have chassis legs barely attached to the car.
In my experience, older Mercs don't suffer badly with electrical troubles, but its best to check carefully with any old car.
Personally, I wouldn't be worried about buying one with plenty of toys. If things go wrong there are always plenty of cheap second hand spares available.