Fuel Filter plastic O-ring !
If you replace your Prism's fuel filter yourself, be "EXTREMELY" careful removing and reinserting the fuel filter's "fragile plastic clip ring" or O-Ring, whatever you call it, on the fuel input line connector. Can't believe Mercedes did that.
RV shops are really bad about making you leave your RV there for 2wks for even something as easy an oil or fuel filter change. So I do these repairs myself. Took me 2hrs.
With a Mercedes its good for you to know how to do the simple maintenance repairs. You sure don't want to be stranded out on a trip. I read so many unfortunate stories of folks having to leave their RV at shops for a week or more when they're on a trip. That's the down side of these Mercedes. Mine tried to strand us twice, but I got the upper hand. (Mamma is sure grateful to have me around on those days)