When I was doing a little research on what to do about the cracked drivers seat I have...I looked at custom fit sheepskin covers (
http://www.sheepskinexpress.com/mercedes-benz.htm) - but, the trouble was, they're nearly the same price as new vinyl for my seats (
http://gahh.com/). When picking out the particular seat covering from GAHH, you specify the options for which version of the seat you have, and whether it was leather or mbtex. With that information, they should be able to do mbtex in place of the original leather (for the front seats, the difference is $1322 vs $832). Prices for the back seat look comparable.
With that said, I'm not sure which other trim pieces are leather, too...
Is your car smoked silver / medium red? Mine is
