The bolt pattern is 5mm x 112mm. It is common to most Mercedes Benz cars, including yours. Where you want to pay particular attention is to the "offset." In general, this refers to where the wheel will sit once it's bolted up. Too far into the car, and the wheel will be rubbing against front end components and the like. Too far away from the car, and the tires will be rubbing the inside of the fenders. So...choose carefully.
I believe that your car has a 20mm offset. You'll see it sometimes written as "ET 20." My car is that size. I've attached a picture so you can get an idea what a rim change might look like.
1980 300SD (Anthrcite Gray) 253,108 miles
1982 300SD (Silver Blue) 242,398 miles
1982 300SD (Black) 263,185 miles