I can respond to your second question.
I have a '92 300e with 2.6 engie that had an annoying vibration at idle, especially at a stoplight with the car idling in drive. The engine ran smooth except for the vibration so I suspected the motor mount was the culprit. I put on a new motor mount from Fastlane and the car feels like new now...virtually no vibration.
I read that sometimes a failed motor mount will ooze fluid. Mine didn't. The only evidence was that one motor mount (the bad one) was a little more compressed. You can compare by feeling the rubber spacer on the bottom side of the mount.
Hope this helps.