Hi Deidra, welcome to the forums! If you have active mold growing on the inside of the trailer, I'd start with a solution of bleach water (1/2 cup to a gallon of water or thereabouts), wear a respirator and gloves, long sleeves, hat, and start scrubbing it off. If it's old mold, use a vaccuum cleaner with a good HEPA filter, respirator, gloves, and vaccuum off as much as you can, then scrub off the rest as before. You never know with mold what you have...
For restoration, and rebuild ideas, click on the forum links to the left, pick your subject and start reading. There are lots and lots of us out here doing the same thing you are. We had mouse leavings instead of mold to contend with, but it's still pretty icky to get it all cleaned up! Good luck and post pictures!