Pop Up Camper roof repair/rebuild

The rear was hacked together by the previous owner and he plastered the whole thing with caulk that was already pulling away by the time I got hom. I was going to remove caulk and silicone it but saw the damage to the aluminum and have decided to fix or replace the back aluminum piece. I think I am thinking of cutting the aluminum off about 2 inches below the top edge and slide a new piece of aluminum under the remaining aluminum put dicor tape and silicone it then put the drip edge back on that goes along the top. This piece should cover my seam I create. I plan to use Dicor tape then paint it with the truck bed liner or use silicone if I don't go that route. It seems like the best option, especially for the rear roof wall as it is pretty damaged.Here are pictures of rear roof wall:

The roof itself is styrofoam with a wood trim around the edge and two pieces of wood spanning the distance from side to side. Both rotted on the passenger side. I am not sure how far in the rot on the wood 'beam' spanning the distance from side to side as I cannot get to it. I have removed the wood form the sides of the roof as they were rotted; not sure what to do with the wood support 'beams.' The back third of the foam on one side is wet. I am told that the white foam does not dry out!