Motor Mount Replacement?

TLDR: How to know if my motor mount needs to be replaced?

After having a shield for my catalytic converter installed by an independent mechanic, there was a sporadic muffled grinding noise while the ICE was on. When I took the car back to have the shield adjusted, the mechanic was able to fix the problem by adding spacers to the bolts that fastened the shield to the underside of the car. While adjusting the shield, the mechanic noted that the rear engine mount was "torn". He speculated that the engine was shifting (due to the broken engine mount) and causing the catalytic converter to rub against the cat shield.

Now that the mechanic has added the spacers to the cat shield, the car appears to be running normally with no unusual noises or vibrations. Should I replace the motor mount even if I can't tell that anything is wrong? If I'm going to have this done, should I replace all of the mounts at once or only the torn rear mount? Would aftermarket mounts be acceptable or are OEM parts superior?

I searched online but I haven't been able to find any references to replacing the engine mount for a gen 3 Prius. There is some discussion of doing so for a gen 2 here:
Motor mounts | PriusChat

Background Information

• My car has 190k miles
• Engine replaced by Toyota dealership at 175k miles. Used engine had 35k miles at time of installation.

 

Re to Bisco: The mechanic quoted me $500 to replace the rear motor mount. The mechanic pointed to the motor mount with his flash light while the car was on a lift but I couldn't tell whether the motor mount was broken or not.

Re to Georgina Rudkus: That makes sense. I'll go for OEM parts.