well, we definitly know it can be done, FDF did it for their wonderful mod and it looked fantastic. Civil war mod also changed the GUI to stunning effect. This is something I would really like to see a tutorial on, on the other hand if i can figure it out myself I might make one.
As for dialogs, get a description.ext tutorial, Vektorboson's text tutorial and the dialog editor by razorwings and you can really hit the ground running. As a fellow newbie I would like to offer my encouragment and limited knowledge to anyone who wants to get into dialog editing, it can really enhance a mission.