Purchased a Hearthstone Clydesdale having the place I purchased it from Ashwood fireplace in Patchohue li ny install it. Was going to tackle it my self but with the tax savings of a capital improvement it didn't make sense. They are charging $750 for the install and want to make sure it is installed right w/o any corners being cut. I'm saving about 350 in taxes having it installed. Just wanted to make sure it gets installed correctly I have a masonary chimney 13 x 13" clay flu they will be installing a 6" stainless liner 18 ft to the top. How should it be insulated? ( Installer mentioned sealing at top of chimney and at the damper w/ sounded like regular R30 fiberglass not Roxul which I read on here should be used? I asked if there would be a metal block off plate at the damper which didn't seem like they are going to install one...If there is no block up plate what will prevent the insulation from falling onto the insert is this a possible fire hazard? I have natural stone around the opening which sticks out wanted to know if it could be mortared in to avoid seeing gaps didn't seem like installer wanted to bother. Would rather not grind bricks in case I ever sell house and remove insert I also have a Vacu-stack on my current chimney to eliminate a down draft (came with the house I bought last yr) not sure if it's needed anymore? Installer said I wouldn't need it but I wasn't confident in his answer. I will attach a few pictures of the stone and chimney with vacu-stack below. Any help would be appreciated!!