That was good, I was worried about removing such a large mirror all at one time.
Those vents should not be a big problem as long as they are not directly behind your TV.
Perhaps an AV expert can give some advice here on mounting, etc.
Nice stone work, it gives you a whole different feel to your great room I am sure.
We have a stone fireplace in our great room and sure enjoy it on a cold evening in the South.
Wife: "You can buy anything you want when you redo this house."
Husband: "Could I get that in writing, dear?"