The blower is located in the back (as you probably already know from the noise) and requires a bunch of screws to be removed to get to it. I have this same range in my training kitchen and will take some photos tomorrow and will post to give you a bit of a visual reference.

Well I took the blower out of my test kitchen oven (first time I had to do that) and I hope yours is easier to do. The early models required less contortions than the new ones so I am keeping my fingers crossed for you. The process to get to the blower is pull the unit out so you can get behind it and remove the screws (4 each) holding both cross braces in place. Then remove all the screws holding the center back panel on and remove it. Then there is a panel just above the center panel that runs from side to side and had the gas and electrical connections running through it. This panel needs to come out which will expose the blower. If you are lucky, the blower is held in place with four screws that you will be looking at. If yours is like mine, there are three screws in top and two screws on the bottom that come up from under the blower. You will need a small ratchet to get to these. It looks like four screws under the blower, but only the front to need to be removed. Then change everything and put it back together. I also took some photos that are rather large, so if you contact me at my website I can email them to you.