Can someone possibly give me a definition of trimming loops in the pro-surf program?

A trimming loop is a generic surface limited by lines/edges. If you have errors in trimming loops, you have errors in some surfaces. Simple shapes can be created in pro-surf, but you might want to go back to the CAD program and have a closer look at the places the errors occure. Sometimes an automatic fix will clean the surfaces, and it's always good to automatically fix, increase the tolerance (e.g. by 2x) and rerun the automatic fix and so on. With "vdis xx xx" you can get an idea about the distance between two vertices so that you know approx. how far you want to increase the tolerance. When you select points you will see the vertex number in the select window or in the main window.

Hope this helps!