I am assuming the w116 300sd has a similar engine set up as my car, so here goes. The crankcase plug is located at the back of the oil pan on the left (driver's) side, you need a 13mm socket. The block drain for the coolant is located on the right side of the engine. It's near the viscinity of the turbo. It's easy to reach if you remove the plastic u-tube going from the air cleaner housing to the turbo. I think you need a 17mm socket with an extension and sometimes a cheater bar. The drain at the radiator is located at the bottom left corner of the radiator. It's a plastic, light blue plug which can be removed using a phillips screwdriver. Good luck.
'82 300D Turbo 216k miles