My 05 Maxima SE (25,000 miles) , when hot, sometimes sounds like a
very rough diesel at idle and row RPMs.

A dealership mechanic finally heard the vibration (I happened to be
near the dealership when the problem re-occured) and said it
could be a bad engine mount. I'm supposed to take the car
in tomorrow.

The car has been doing that for several months (dealership was
never able to confirm it before today), any chance that some damage
has already occured?

Thanks a lot!