Greg, it's best to use the black MB sealant when replacing the upper timing chain cover ... just a dab in the recesses at the ends of the horseshoe gasket. Reinstalling the valve cover without knocking the half-moon sections of the gasket out of place is tricky. It's best to use an inspection mirror to ensure the gasket and valve cover are seated properly. Hopefully the head gasket is not shot. The head gasket on our daughter's 1991 300CE is shot (confirmed by a local independent tech who charges $1,500 to replace) and it leaks oil badly ... small puddle of oil quickly appears when she parks. That's a job I'm apprehensive about, but it will be a wonderful learning experience.

__________________
Fred Hoelzle