300SDL What is this gasket and the torque specs?

[julio.garcia.fc]

Sorry, I know this is a really dumb question, but I am still figuring my way around my car. What is this cover called and how tricky is it to replace this gasket, assuming I should? It does not look too bad. I am not quite sure what to search for in the forum.

I have been working my way around various leaks and other minor issues and my engine seem pretty clean now, except for this leak. As I checked the bolts around the cover, I noticed that 3 of them were essentially loose. I could turn one of them one full turn by hand! I went around and tightened everything as tight as I could with my hand on the pivot of the wrench, not the end, so I do not expect the bots to be too tight (30 years of computer programming have not given me strong hands). How tight should they be? The head gasket was replaced 70K miles ago and the car has 270K now.