Wow. Nice work. I helped my in-laws do a very similar remodel. Father-in-law took it down all the way to the outer skin. We replaced some of the framing (from the inside) and never removed the outer skin. Unfortunately, we didn't have an enclosed area to work. Ours was done outside, in the middle of the summer, and it was HOT! The end result was nice. But it was a MUCH smaller trailer too!
You did a great job there. Why sell it? You've just built your self a new trailer that will probably outlast everything now! After all that work, you should enjoy it now ... for a long, long time!