Here at the FastLane:

Vehicle: 1983 Mercedes Benz 380SEL
Part: Valve Stem Seal Kit
2 per engine
Fits Engine: 028838-

A8069-26467 Valve Stem Seal Kit $9.40

Plus valve cover gaskets.

This is just the seals, not the guides, labor shouldn't be $580.

OR

I'll do it for $500