Neiladin, except for the high price of the oil and filter, it really is one of the easiest cars I've had to change the oil on. I don't even jack the car up. I've got a couple of 2"X10" boards that I pull the front wheels up on, and that gives me enough room to reach all 4 screws to drop the under body splash pan.
The trickiest part is when you replace the O-rings on the filter cartridge bayonet, just make sure you get them all back in the proper position. Especially the top one. Because if you don't, the entire engine bay gets "oil sprayed".
The cheapest place that I've found the oil is at Wal-Mart, or AutoZone. The filters can be found at the D/C dealership, or at the Mercedes dealer. I usually figure on paying about $60 everytime I change the oil. I change my oil every 3,500 miles. Good luck