The valve cover grommet/bolt seals are on this page, quantity needed 12:
1993 Mercedes-Benz 300E Base Sedan - Cylinder Head & Valvetrain - Page 1
This is an easy valve cover gasket to replace. Use an inch pound torque wrench for tightening and do not over torque the bolts. The bolts that hold the coil/spark plug cover in place are often already stripped.
In the diagram the large gasket around the perimeter is the valve cover gasket. The six round seals in the center are spark plug access hole seals and the two half moon seals go at the back of the valve cover. You will understand it when you have the cover off and see it.
Some will disagree; but, I would put a
small, sparing amount of black RTV around the half moon seal edges.
This car is from the era of engine wiring harness problems. If you do not know if the harness has been replaced try to find out first by inspecting it for cracked insulation. If it has not been replaced and is cracked you may wish to hold off on doing the valve cover gasket until it is confirmed that the valve cover is leaking. if the cover is not leaking and the harness is disturbed to change a non-leaking gasket a problem will be created instead of solved.
If you need a harness send me a PM, hopefully you do not and yours has already been replaced...many have.
Good luck!!!