1995 Audi A6 Quattro Question: Engine & Transmission Mount replacement

My car used to be so quiet when I turned on the engine. So quiet that sometimes I would switch it on again forgetting it was already on. That was a 100k miles ago. Now it's not as quiet and I definitely can tell the engine is on with a little vibration, with 170k miles on it, that is expected and acceptable, don't you think? I had an earlier post about the coolant reservoir replacement, now that that's resolved, my new mechanic tells me the engine (L & R) and the transmission mounts (both) need to be replaced because they're getting old and loose hence the vibration. There were certain services on my car that my old mechanic suggested to ignore, unnecessary repairs on an old car is truly a waste of $$. For as long as it did not affect the car performance/engine, leave it alone. (1) I want to know if replacing the part in question is one I can ignore, after all, the little vibration I feel on the car is not really bothering me? (2) How much does it normally cost for this kind of service if I took my car to an Audi Specialist? (3) Can you please recommend a trust worthy one within 15-30 miles from 92336 area code SoCal? Thanks in advance.