RE: DIY Repairs and Maintenance
You should be able to change the oil/filter with no problem. Check your owners manual for oil type/capacity -- MB recommends Mobil 1 0w40 (meets MB's spec 229.5) but also lists other synthetic oils. The oil filter can be purchased from several online vendors that carry oem MB parts (~$16). There are two methods of changing the oil, and you'll see many posts on the MB forums that pretty much split 50/50 on the methods -- I prefer to pull the plastic panels under the oil pan and drain the oil as this gives my an opportunity to inspect things under there. I think you may have a composite oil filter cap assembly which I would recommend you buy the "proper" filter cap wrench (Hazet or from AST Tools) -- if you crack that cap assembly you will have to buy a new one from the dealership -- I don't know any online vendors who sell it.
The air filter(s) are also easy once you figure out how to get them out of the air box. I'm not familiar with your model but on my '03 E320 the airbox just lifts off and snaps back into position -- the two filters are in a couple of compartments that are fastened with Torx screws.
You can also change the cabin filter(s) once you find where they're located.
You can change the fuel filter if it is accessible (mine's in the fuel tank!!) -- a word of caution here -- the fuel system is under high pressure so you can't just pull the filter off unless you want a very dangerous gasoline bath!!! You will need to find the fuse or relay for the fuel pump and pull it and try to start the car -- this will lower the fuel line pressure enough to change the filter, and don't forget to open the gas tank cap to remove pressure built up in the tank. If this sounds like you don't want to do it, then have a pro do it.
Someday, but not soon, you will be able to change the long serpentine accessory drive belt on your engine. I also recommend that you change the idler & tensioner pulleys when you do this. This is the analogy to cars that have the external cam timing belts.
I'll guess again that you probably have 100K miles platinum spark plugs. I have had several cars with these -- I change them at 50K miles because I've heard too many horror stories of spark plugs being stuck in the aluminum cylinder heads after 100K miles even though the plugs had a nickel coating on them.
Brakes: if you have the SBC system for your brakes, check the other forums as people have figured out a way to change the brakes without going to the dealer and having the SBC disabled -- YOU CANNOT WORK ON THE BRAKES WITH AN ACTIVE SBC!!!!
With that aside, brakes are fairly easy to replace including rotors, pads and sensors and OEM parts are all available online.
That's about all I can think of, and probably all that we can do with cars nowadays. Good luck and if you can't find answers here, check some of the other MB forums. Once you get your repair manuals, your questions will be answered.
2003 E320 owner -- first MB!