Don't have that model, but if mine was any indication, you may not need to cut any holes out. Just remove the distribution/converter panel, as there will probably be quite a bit of room behind it to install your unit.
Have the panel removed from the wall and the Progressive unit wired to one end. I purchased a five foot piece of the same cable used in the trailer from Lowes, so didn't have to cut the trailer cable.
I mounted the box to the outer wall where the light is shining
I then mounted the remote display to the right of the panel, so only had to cut a very small hole to bring the cable through the wall
Another good thing to do while the power is off and you have all your tools out, is tighten all the 120 volt and 12 volt connections in the panel before turning the power back on. I didn't disconnect the 12 volt power, but that is your choice, just depends on your comfort level.