Howdy and welcome to airforums.com, Cowdeevas (love yer handle!)
I think that while you will find lots of great advice and help finding the trailer of your dreams to accomplish your task, the first thing that struck me is that the real challenge will be to modify the bones of the trailer to make an interesting store, while keeping it in a condition that will allow it to be towed and used without any structural failure.
Or even just to have large crowds of excited shoppers in it, safely.
You see, Airstream trailers were designed in a way where the floor holds up the ceiling, but also the ceiling holds up the floor. It takes careful engineering to remove big chunks of the hull without endangering the frame.
Even if you don't put large holes in the shell, you have to remember that the floors are built with 24" spaces between the supports. A house, as a comparison, has 18" spacings. To me, it's quite believable that several extra-large shoppers, if standing close together, could actually go through the stock flooring, especially given that you might pick a unit that's say, as old as mine, and hasn't been refurbished.
I'm not trying to scare you, but I would hope that you will consult with people that have good experience with Airstream construction, so as to have a safe vehicle in which to sell your bling.