My husband and I inherited our fireplace from the original owners of our condo. We are remodeling and have torn out the surround. We want to replace it but aren't sure how much non combustible material bust be in the sides before we can use wood. Everything I'm reading says that we need to follow manufacturers instructions, but we don't have that paperwork and we can't find any identifying information on the fireplace. Any tips on how we. Can find out how we need to approach this? Thanks for any help!!