If you're really going to do this yourself, be forewarned, the worst problem I had was in pulling the cover. Many of the bolts holding it on have, instead of nuts, a metal sleeve pressed into the plastic cover on the back side. If the threads are sufficiently frozen, what will happen is that the sleeve will break free from the plastic and just spin, making it impossible to unscrew the bolt.
I wound up taking a hacksaw blade, and cutting the head of the bolt off, and then replacing it with a new bolt and nut when it came time to reassemble. You will need to remove both fans and their housings to get to some of the bolts.