This was the first time replacing the fan. It is a lot easier to work in the oven compartment with the oven door removed, only two screws on the door and the hinges were released. I found that a couple of the screws were either rusted or stripped so I used a pair of pliers to remove the screws that were holding the diffuser in place. Once there was access to the fan I found that the fan was warped and that the blades were scraping against the back wall of the oven. The next challenge was to remove the retaining nut. I used a sheet metal screw to secure the warped fan to keep it from spinning. once I figured out that you have to turn the retaining nut to the right to loosen, it came off easily. 1/2" socket with extension. When I replace the fan I used two washers for spacers to make sure that the fan would not scrape the wall of the oven. Its been tested many times and the oven does not make that horrible sound anymore.