Question: I bought a 10 year old house last month and am new to the area. We had a chimney sweep come in to clean the chimney but he said it wasn't needed but pointed out the rear wall of the pre-fab fireplace was broken. It is cracked horizontally and is really just two pieces sitting against each other and stated we should NOT use the fireplace until the rear wall is replaced. . It is a Martin (SC36) or Aspin (HC 36A) model. He stated he'd check the price but thought it would run about $150-$200 to replace it. Of that $50 would be labor. It looks to me as if the rear wall simply lifts out and I can replace it myself. Is it a tough job or unsafe for me to do myself? Answer: You are correct. It just sits there, usually under a small sheet metal tab. Furthermore, it should only cost about $75. at most for the part. A crack like you describe is little reason for concern, since the actual wall of the fireplace is made of metal and behind this brick. I would leave it alone until it actually falls apart...or, buy a caulk tube of fireplace mortar and patch it.