I have a 1986 300SDL and a 1987 300D. Engines are pretty much the same. If you can work on your '87, you can get this guy to start. The 126 body is bigger, an older design, but a very fine bit of work. Get the SDL running and you will love it. If it has been maintained by the dealer, there shouldn't be too much wrong with it. Check the casting number on the side of the head and let us know what version it is.
Hope you take the car, you will love it. (and if ya don't want it, one of us will be gLad to take it!)