If you're getting the "low oil level" indication on the display, there's a good chance it's NOT the sensor but the electrical connection on the side. The sensor is located on the driver's side of the oil pan. Just remove the panel from under the engine and you'll see it right there.
I had the same problem and in my case, the wire had simply snapped inside the connector due to vibration. It's very easy to unsnap the cover off the connector, clean the metal parts thoroughly, strip the wire back a little and re-solder it.
One nice thing about Mercedes is that many of the parts and connectors are servicable.
If it turns out that you need another sensor, I'll sell you a brand new one (mint in box
) for $80 that I bought here by accident when it was actually the wire...
This is of course it the E300 part is compatable with your car.