Welcome from another
Scamp 13-1 owner! We’ve loved our 2008 for over 12 years now.
Ours also has
light surface rust on the frame, pretty typical. I touch up the tongue and bumper every few years for appearance, but I haven’t done anything to the underside. Because our climate is so dry and we have garage storage, it doesn't seem to be progressing much. In a wet and humid climate like yours, it might be worth taking some action, but I don't think it's urgent. POR15 is the product many use. It’s an unpleasant and messy job.
I also replaced the gravel guard hardware with a new set from Scamp. Ours was not only rusty but also worn to the point the latches were loose. Not sure, but I think it's the same hardware used for old-style wooden screen
windows, so you might be able to find it at a local hardware store.
Cutting another door in the closet by the door is a common mod. Just stay away from the corners and the wood stiffeners that are fiberglassed to the inside. That closet is structural and helps support the roof and maintain proper curvature of the door opening. Does yours have the big bed option?
2018 was the first year for the black door hinges. Early builds were cast aluminum and prone to fracture, leading to numerous doors separating from the body (a few fell off under tow). The upper hinge usually fails first. The solution was to switch to stamped steel hinges. Many have already been changed, but check yours with a magnet. If they’re aluminum, contact Scamp regarding steel replacements. I hope they’re still stocking them. They discontinued those hinges on new builds in 2021 with the door redesign.
Best wishes with your projects. Happy camping!