Hello wood burners. I'm getting ready to order my first wood burning stove. While preparing I noticed I have an old heatilator insert (not sure if there is masonry behind it). I've heard conflicting answers if I can install a insert inside of this metal. Seems Rusty, but pretty solid overall. Any suggestions? Would be too big of a job for me to rip it out especially to find no masonry behind it. Is my only option to buy a zero clearance insert? Thanks for any help