coil spring

Depends on your location, for where to get. Usually requires the use of a spring compresion tool to decompress the new spring, prior to fitting

Reference # 6218 From $73.25.

And they will rent you the spring compressor tool.

Yes, you need the Mercedes spring compressor tool to do the job. If you are doing one, you might as well do all 4... However, you must change a pair at a time, you cannot just change one.

Be very careful. Handle a compressed spring like eggs.

A compressed spring releasing suddenly can kill you or a bystander.

Or maybe like a bottle of nitroglycerin.

You should change all four springs for consistent handling, and certainly both front springs at the same time or your car will not handle properly. I have changed all four springs in my 1982 300 TDT, and it handles like new. I do almost all my own work, including removing and installing the engine when I had it remanufactured last summer, but when I changed the springs I had the dealer do it because I didn't want to get hurt and compressing those big Mercedes springs is dangerous. The labor for each pair was about $400 at the Mercedes dealer.

The alternatives are wrecking yard parts or after market, although those will be expensive compared to the former.