Originally Posted by @K6GAD
There are two removable panels in the rear compartment. They form an "L" shape with the forward bulkhead. Remove the smaller one that faces the right side of the motor home. There should be 6 or 8 screws. Some in the bulkhead and the same number in the other panel facing the rear of the compartment. The filter is right behind this smaller panel.
Just to help this discussion along, I attach a picture of the filter with the panel removed.
I am not crazy about this design, and may think about modifying it, but i am not sure you have to change the filter often enough to make it worthwhile.