is it posible to short out an ECM while reconfiguring a new mass air flow sensor? on 2000 Nissan Maxima

I recently had the dealership replace the mass air flow sensor. The next time I started it I noticed a strange mechanical sound when reving the motor and when turning it off. I took it back because the check engine light also came back on the day after. They are telling me it is the electronicly controlled motor mounts and possibly the ECM. Could they have shorted out the ECM when they reset the mass air flow sensor? I don't trust the service manager that is incharge of my car.

Asked by for the 2000 Nissan Maxima
I presume the faulty Airflow meter had set a code that had initially brought on a Service Engine Soon light. I forget the code but it signifies lean air fuel ratio with a 30%+ fuel trim figure. When they pulled codes initially on replacing the air flow meter did they note any other codes present at that time?
Replacing the airflow meter is simple I can't see anyone screwing that up. Ask to have codes, pending codes and freeze frame information recorded now for your records. Perhaps get another opinion from another shop.
Oxygen sensor/Air fuel ratio sensors were a problem with these. Airflow meter problems do result in a loss of power, decreased miles per gallon and a Check Engine light.
The codes when I took it in were front 02 sensors but now the codes are for the rear 02 sensors. The power is back at higher rpm's but it is still sluggish when cold. thank you for your help!