I want to install a woodburning stove in a prefab gas fireplace. I had an installer out to look at the job and he said the existing firebox was to small for any insert and suggested putting in a woodstove but he didnt want to use the existing fireplace but to install one in another area. I have a metal fireplace and an 8'' metal pipe going out.I was told to run a 6'' stainlesspipe through the existing. He was no help. I would like to use the existing area. I would appreciate any help