how do i change the catalytic on Grizzly

Hoping someone here can help as I cannot get my hands on a manual.

We recently purchased a home built in 96 which has a Derco Grizzly insert. It works GREAT, but recently seems to be performing worse and worse.

The catalytice converter may need to be replaced, but it appears to be held in place by a cover which have 4 brackets holding it in place. These brackets do not seem to move, and I do not want to damage anything by trying to force it. So, I thought I would ask here first.

Recently, one of these brackets that holds this in place came off today too. It appears it was welded on, but that would prevent changing the catalytic converter. Any information would be appreciated.

There are a couple other folks with Derco on this forum, such as: http://www.hearth.com/talk/threads/derco-insert-resurrection.62415/

Maybe connecting with them will get you what you need. I see Derco Grizzly cats for sale at quite a few online places - maybe these guys have the install info you need for your model.