I just re-screened all mine on a 78 Argosy. Purchased everything at Home Depot. An inexpensive tool for screens to push the spline (rubber material)back in, utility knife, clamps and screen material.
If you have a friend you will not need clamps. I do not have friends, LOL, so I purchased clamps that look like giant clothespins. They help to keep the screen taut while rolling in the spline.
After removing the old spline and screen, oversize the new screen a couple inches around the frame, place on top of the frame, use tool to push screen into the slot, start installing the spline and use other side of the tool to roll it in to the slot, have friend help to keep taut. Continue to roll the spline in until finished. Trim spine and screen material.
1. You can probably reuse your existing splines as your trailer is newer.
2. Your tool may have the spline roller (pizza wheel with the groove) that has one side slightly larger than the other. Keep the long side to the trim side. Ask me how I know, If you use it in reverse, there is a greater chance of cutting the screen as you roll the spline in.
3. It is very easy, take your time rolling. As the spline is getting recessed it pulls the screen taut.