I am trying to help a friend who wants to install a flexible liner on his old Ashley insert. I have not seen it and have no pictures, but was told it has 2 exhaust openings on the top about 3.5" x 7.5" and they are separated by about 11" from one another. All I have is a model # A1B3624A1. My question is how would attach an exhaust pipe/liner attach to this insert, or is it past its useful life?