A Porta-power is what you need to fix that roof. I'd try that first.
A friend of mine had a big limb fall on his cab. He is a short fella but still couldn't sit in the seat without bumping his head.
He was ready to push the truck into the swamp until his buddy brought out the Porta-power and pushed the vast majority of the dent back out, then with a hammer and dolly got the top back to where it belongs.
