indeed. dialogs look pretty complicated - they're dealt with in the
advanced scripting board - but once you figure out the bits you need, i.e. a combo box, or buttons, or pictures, then the rest of it is just a very tedious process of getting the things in the right place on the screen, much like object placement - move it, preview, abort, move it a tiny bit more, preview, abort, move it a tiny bit more......
this tutorial is the one i used to learn dialogs. there's also a handy
dialog maker which takes a lot of the tedium out of the task. both definitely worth a look.
good luck - dialogs are tricksy at first, but they add such a dynamic element to flashpoint missions, everyone should learn 'em