I think replacing the Ensolite would be a really big job. I wouldn't do that unless it was absolutely necessary, myself. For one thing, the old contact cement/glue is a real bear to get off the shell (at least mine was, and I'm only doing small areas where I'm tabbing in cabinetry -- I'll be re-adhering the Ensolite when I'm done). Then refitting and regluing the whole trailer..... that would not be an easy job.
Good to know about the Scamp seam tape. I had my doubts based on the price. I would rather spend a bit more and get a tape with a higher-tack glue than I would to use a hot glue gun. U-line does have some better looking tapes.
For removing glue residue, I have a standard arsenal of things to try. One of them usually does the trick (although removing the contact cement residue that held original Ensolite onto the Boler
took a two-part approach; I was about to tear my hair out on that one). Of course, for any of the things on this list, wear appropriate protection and try in the ol' inconspicuous area first.
3M Adhesive remover (black aerosol can; smells like orange)
If it's a sticker/label, using a fresh piece of the same sticker to pull off the adhesive
I'll probably think of some others to add.