99' E320 oil level, ignition switch and Headrest cover

I just purchased a used 99' E320. The dash message says that the oil level is above the max, although the dip stick says that the level is in the middle of the normal range. What might be the problem? The key switch lock ring which holds it out flush with the dash is loose and when the ring comes off it lets the switch drop behind the dash. Is there an easy fix? The bottom of the driver seat headrest cover is loose and internally there is a black plastic piece which was apparently used to hold the cover in place which is broken. Can I remove the cover and replace just that piece?

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The oil level/quality sensor inside of the engine is sending BAD info to the instrument cluster & that is somewhat a common failure of the sensor.