I have several previously written Photoshop JS scripts which I'd like to run through buttons on PS panels, much like the example for the HelloWorld introduction. I assume that--using external interface--I'll somehow be able to fire off these script files. Is this a correct assumption?
Certainly, but not with external interface.
Have a look at the cookbooks. There are examples of how to use the root host object to call directly into extendscript.
Will do. Thanks for the tip.