I'm not sure of the Mercedes shop manual spec. for your pan. Mine (for the 560SL M117 engine) calls for a bit of grease on one side of the gasket, probably to hold it in place during mounting.
I read a bunch of threads here discussing this subject, and the consensus was to use sealant anyway, with a whole range of 'what kind I use' recommendations.
On the SL, you have to drop the entire front end subframe to drop the pan. I didn't ever want to go there again, and I also noticed a very, very slight misalignment of the rear flange with the engine pan mounting surface. Someone had applied waaaay to much sealant to try and correct a leak there, the cheap black stuff. Several huge chunks fetched up in the oil pump screen.
I went with a thin coat of Permatex blue on the pan itself, to glue the gasket down, then another thin coat on the gasket to seal to the engine/flange surface. I applied a bit more in the rear corners where the sealing area is very narrow.
I let the engine drip overnight after removing the pan before final cleaning and gasket/replacement work. I used brake cleaner and laquer thinner as cleaning solvents.
Pay close attention to the torque specification for the pan bolts.

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1986 560SL
2002 Toyota Camry
1993 Lexus