I'm not Yvon, but I'll chime in and say that you cannot remove plywood from resin because it's a coating. It would be like "removing the wood from the varnish" - not possible.
When you put in new wood you can re-coat it with resin (and/or add fiberglass cloth or reinforcement, as suitable). This is in general, since I can't see your specific trailer.
Oh, and resin alone will not be enough "glue" to hold a floor down. You would need to tab in with cloth, or use fasteners, I would think (again, not looking at your trailer).