first thing is call 1-800-MERCEDES and order an owners manual plus a Mercedes booklet for Factory Approved Service Products. Seriously, a must and cheap.
Also Haynes Manuals sells a Service and repair manual for the car, english UK version but very good.
I have a C230 so things SHOULD be close
Car takes about 6.5 quarts
Mercedes OEM filter, canister fits under the black oil filter housing top, Mercedes offers a ten dollar socket that takes it off. Filter comes with a rubber gasket that fits on oil filter cap that needs to be lubricated with oil and put in place of old one.
OIl drain plus is 13 or 14 mm, and the sound encapsulation panel that needs to come off is either a 9 or 10 mm socket Get a little copper drain plug washer.
Mercedes vehicles can be drained by sucking oil out of the dipstick tube, neeeds a device like a TOPSIDER tm. easy and works well.
Oil should be warmed to operating temp, oil filler cap has a rubber gasket that can leak and shoud be replaced every 10K miles, or a new cap for a few bucks might be easier to get.
this site in the DIY section shoiuld be more specific on how to do an oil change, even if not your car model