I suggest you start with the frame. If you have loose or bad bolts, the continued movement as you tow will damage any repair you do to the shell.
Then work on the needed roof support so the shell keeps its shape and is sturdy.
Next I would repair/ clean up the shell so that it is weather tight.
After that address what you need to tow safely. There are some ways to attach lights
that are not permanent, but will let you tow safely.
Once these are done, I say pack and camp. Take along a notebook or journal and notice what you want or need to be comfortable.
After a couple of trips you will know what to do next.
Do remember before your first tow that loose items move around A LOT when these little campers are in motion. I suggest using plastic containers to hold your stuff and bungees or tie downs to hold the containers. Just don't anchor items to the fiberglass walls, they don't do well with sideways forces.
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