The outer shell is easier to deal with than you might think. All you need to do is remove the back casting. The clean-out and re-gasketing is quite easy. A LOT easier than removing and re-installing the two piece fireback. That is a filthy mess of a re-install that offers little room for maneuvering. I would suggest doing the fireback (if needed) and back casting at the same time since the fireback install would be a lot easier to do when the back casting has been removed.
Good to know. I was thinking that I could probably take the flue collar off and get more room to reach the damper gasket that way, but if the entire back casting comes off easy why not. I imagine I need to get that off to replace the refractory anyway if the upper fireback doesn't come out...... I see what you mean, it does look like getting the upper fireback out would be a real *(&^^ even though its smaller in the 2550.
The stove heats just fine and Im sure I could get a few more seasons out of it before the refractory is totally shot.... but I know its getting to be due and Im crazy enough to want the challenge.