If the existing insert has never been pulled for cleaning, and it is a true slammer install, you most likely are going to find a ton of crap that has been swept down, but never cleaned out over the years. Not a good thing, and a blaze waiting to happen.
Yeah when I cleaned there was a lot of creosote back there. Not a good feeling... Wondering if I should just line the chimney and keep using the smoke dragon with a new liner?