I'd never written any GUI code before the
SCJD project, although I had used GUI-builder tools like JBuilder and Visual Cafe. I think that they are OK, but they generate terrible code. I think it's better to write the GUI yourself for SCJD - I found it hard and frustrating to begin with, but it does get easier.
Try reading the Sun swing tutorial to help understand what widgets are available, have a play with the various layout managers (I used BorderLayout for the simple stuff and GridBagLayout for panels with lots of buttons and labels) and be prepared to experiment. It's a good learning experience