Hi Andy -

The sensor is an easy bolt on/plug in piece. It is located in the bottom half of the oil pan. The pan is in two parts. They are held together with a 'form-a-gasket' type seal. I believe MB has a spec for the sealant but maybe others have found something that works just as well.

A quick check of the oil level via the dipstick should remove any concerns.

HOWEVER, it may not be the sensor. The W210's are sensitive to battery voltage. Once it drops below a certain point it's common to get false positives for various sensors as well as loss of sync on windows and sunroof. The battery will still have enough to start the car so the old 'see if the headlights are dim' doesn't apply. It the battery is much over 4 years old it's a likely culprit.

Good luck.