Don't worry about a little oil at the bottom of your engine as long as the car doesn't drop pools of oil or starts to use oil. It is quiet normal for a mercedes to sweat some oil.
To avoid your oil pan from touching the road and cracking up, you can install an original mercedes steel carter protection plate. These plates are great and saved my former 190D engines live for 4 or 5 times!
If you come up with any questions/problems while you are working on your dash, just mail me.
...no rice inside...