Join Date: Aug 2013
Location: Montana - Estados Unidos De Americana
The side boards are just going to be screwed in place, or they will fit behind a lip on the end. It really is not hard to replace them, if they are a screw style, just remove or drill out the screws and replace, if they are the lip style you will have to pry them out and pry the new ones back in.
When you replace them use Sanded CDX plywood of the same thickness, be sure to put the sanded side in, it is more expensive, but using non sanded means you could give your horse a very painful sliver.
As for paint, personally for trailers I like rust oleum, you can buy it by the one gallon can, it is cheap, it is hard, it can be rolled or sprayed, and you can get rattle cans for touch up anywhere.
As for the rust, there is a product made by Sherwin Williams called Ossfoa, it is a rust neutralizer, chip off the rust as much as you can, paint it with Ossfoa, then if there are no rust holes through paint over it, if not you will need to figure out a patch.
"Don't just teach your children to read, teach them to question what they read, teach them to question everything" - George Carlin
My Journal: Montana horse adventures