Sourcing filon & roof corner/gutter - please help

Frankly it's going to be worth exactly what it's worth now in its rotten unrepaired condition.

People don't want a "repaired" camper. They will call into question your skill, attention to detail, and quality of workmanship. The assumption will be is that there is a hack job hidden behind all that new filon. It's not people's first rodeo. They've heard grandiose claims about this and that and the other thing being 100%, in great condition, and been BURNED, or know someone who has.