I have a Quadra File CB 1200i and the exhaust blower is making a whining sound. I've read in other postings that the whine might be caused by build up on the blades causing the the blower to be out of balance. I'd like to remove the blower and clean it, but I'm not sure how to get it out. Do I remove the insert from within the hearth? If so, do I need to disconnect the exhaust pipe first? Any instruction on this is appreciated.