If you can handle your BMW's oil, you can do this. Get a 14mm allen key from your local tool emporium. These might take some calling around to locate. Take a quick spin around to warm up the engine. Park it, and unscrew the plug on the oil pan. Drain oil, re-install plug w/ copper crush washer (which should be included w/ MB filter kit). You're done underneath.

Locate filter housing on right side of engine. Loosen large bolt and allow oil to drain. After a minute or so, remove bolt and filter housing. Pull old filter and examine the bottom of the canister for a small rubber washer. That's important to ensure proper oil flow through the filter. Put in new filter, swap out o-ring at the lip of filter housing. Another hose-like rubber fitting should be between the top of the filter and the filter mount. Reassemble and reinstall large bolt. Here's a link of the whole filter assembly for 113 vehicles, which is a very similar design.

Add six quarts of your preferred oil and start motor, keeping an eye on oil pressure gauge. Check for leaks and you're in business. Good luck and I'm sure others will have additional ideas.