foz wrote:
Furnace gets air from three returns. The current door is a hollow core
door but it has a dent in it which is why I want to replace it.

Remove door.

Remove dented panel.

Fill hollow space in door with stuff (Fiberglass, "Great Stuff," polystyrene
packing peanuts, styrofoam, dead cats, etc.).

Install new panel (to match room).

Re-hang door with original hardware, but add heavy-duty weatherstripping.