The fan in our bathroom makes noise. It is a 20 year old builder grade unit that came with the condo. Our bathroom is in the middle of the house, no window. When we removed the fan assembly and tested it with a regular outlet, there was no noise. So, we think it is the fan housing rattling. We cannot find a direct replacement, so we would like to replace it with a newer model, more CFM and less noise. However, we have no access to the attic. The newer model has about the same size housing as the existing one which is nailed to a ceiling joist, but not exactly the same ceiling cutout. We can not even remove the current fan housing without cutting into the ceiling.
What is the best way to replace the fan housing?