I can’t believe all of the poorly installed pellet stoves that I see. 80% of the stoves I am called out on to do a simple service call merit a proper reinstall! They are not sealed, with silicone and screws so they leak carbon dioxide and ash. Folks, don’t expect the so called professionals to do it right either. Most of the jobs I have seen have been put in by paid installers (definitely not professionals). A couple of easy questions you might ask the installer before you let him install you pellet stove insert:

Do you have high temperature silicone?
Do you have metal tape?
Do you have a drill a driver and screws?

If they answers no to any one of these send them packing! There are more questions to ask but this should eliminate the worst imposters.