I am installing a fireplace in a new addition in my home.Its the Quadrafire 7100. I have two questions. Do I insulate the wall behind the fireplace and sheet- rock and then frame the fireplace 2" from the sheet-rock or just frame the fireplace 2" from the insulated wall? Same with ceiling, I am going to 6" tongue and groove car side the ceiling.Do I put the car siding up first to the box the flue goes through and frame the fireplace or frame up first and car side to the fireplace framing? Going to be 6' wide by 2' deep.