Hello. We also have a 1981 300SD. What version is yours? Ours is a U.S. model with California Emissions (makes less power than the standard W126).

We have the U.S. owner's manual. The international manual is better, though. I think CATS can still get you ca copy of it. We got the W124 manual from CATS back then.

First tip: The hood and trunklid are made of aluminum. Take care not to damage them as they need special tools and welding tech to repair.