Greetings. I have a Vermont Castings Sequoia Catalytic fireplace that's about 8 years old. The blower sounds like a blender full of rocks, time to replace. My issue is the openings on the front that access the area under the firebox where the fan goes are 4" tall. The blower unit requires a 5" opening. I cannot get the defective unit out and I can't see how a new one can go in. Am I missing something obvious? I read the owner's manual and searched here and Google, all to no avail. Thank you all in advance.