There is a VALVE COVER gasket on our car.... the BREATHER cover uses a RTV type gasket.... the breather cover is the one that most commonly starts leaking and many here have fixed this at home...there are threads here that show how to DIY...

Quote "A mercedes dealer here told me they were using 5W-40 but my friend in Baton Rouge told me his dealership uses only 0W-30 except on diesels???"

On the oil question, the MB dealer is correct (duh!) on the change to 5W-40. Your friend's dealer is going to have problems if he is using 0w-30 and something happens to those motors.... Use only 0w-40 or 5w-40 synthetic to meet the manufacturer spec... there are several brands that meet the MB spec...