I have a 2010 C 300 4 Matic. The dealer informed me that the engine mounts need to be replaced due to a chassis vibration diagnosed during idle.
He's quoting $ 2,099 including labor and parts. Is this reasonable for this work?

 

You did not mention how many miles you have on your C300, but around 80-120k that is a common cause of vibration. That quote may not be out of line from a dealer. It is a lot of money for a 7 model year old C Class, though. It is also not something that you want to attempt on your garage floor. My suggestion is to find a reputable indy shop (one that flies the MB banner and has a lot of them on the racks) for somewhere around half that price, maybe a bit less. After the change, the car will feel like it is new.

 

7.9 hour job for 4Matic according to factory guidelines. Might be okay depending on their hourly rate but no idea of your location.

FYI for non-4matic it is under 3h job... Hope you get them fixed at some point