I will be installing my hampton gci60 pellet insert soon. In the front of my fireplace there is a air vent that goes through to the exterior of the chimney(fireplace outside air kit?). It sticks up about an inch or so. I think I can just pry it off, but underneath it there is a hole that runs the whole length of the vent 32"x2". What can I seal the with, will insulation work? Or maybe just a piece of plate steel. Also what do I do with ash dump plate? When I slide unit in will it slide the plates off the ash dump. I added a pic