Hi, Dan,
There are no bad questions in this forum. Folks are here to help, and if you're lucky, you'll be able to find someone who has already done what you want to do. This forum is a pretty awesome resource.
You know what's behind my foldout table? The wall! You know what's outside on the skin in the same place? An access door to nowhere! Remove it and look in, and it's the back of the wall behind the table.
You'll find little odd things with your trailer as you go, but see if you can top a door to nowhere.
Lamar