I've replaced 3 mounts on the passenger side, they seem to collapse much faster than the driver side, due to the exhaust heat and the engine torque pushing on them, I suppose.
Passenger side takes about 15 minutes after doing it 3 times, but the driver side is MUCH harder to reach. 2-3 hours flat rate is probably correct - but if they're experienced, they will do it in one.

I developed a Special Measurement Technique for the passenger side mount, to tell if it was collapsed too much. There should be a small sheet metal heat shield over the mount. If you cannot put your index finger between the shield and the mount bracket, the mount is just about ready for replacement.
I wonder if real MB mounts are any better than the aftermarket ones?

I also get that little rumble on acceleration in first gear - seems like a u-joint. Could it be the slight mis-alignment of the center carrier bearing as the engine settles due to to the collapsing mounts?
The most common noise asociated with right-side mount collapse is the banging of the exhaust pipe on the cross brace. It begins first when you accelerate while turning left - very easy to diagnose, sounds like a hammer banging under the right floorboard.

Have them check the rear tranny mount also - they don't collapse near as much - but it's good to look it over - and easy to replace.