It is not terribly difficult to make minor changes, (I have been going through and making all the windows fit on my screen and still show the game window.)
The hard part is figuring out just what you can change, and what you can't.
UIBuilder from my understanding is sort of a "Working Project" and everything that users are capable of is not known.
Add to that, the fact that while the developers are helpful in most ways, there is some information that they just don't even appear to know.
I would suggest that if you are just looking for minor changes, take a look at what is already available for download, somethng might match what you are looking for.
Go from there, make comparisons from the original to what they did in the modification, some will be simple, some will fry your brain
Does that help?
-V-