I plan on cutting this backing board so it would fit into the opening, and holding it in with quarter round or similar.
What would be best for this backing board. MDF, plywood, etc.
Should the mirror be bonded to the backer board. If so how?
I plan to remove the electrical plug, put wire nuts on each wire and wrap the ends in tape. I am going to do nothing with the phone and cable jacks that are there.