Helen, as the others have said really.
Go with an open mind, learn what you can and be prepared to be dis-heartened on the Saturday night and inspired on the Sunday; Pro or Full pass
Remember to fill out the student application form from the GUE website, print it off and take it along.
Bring your swimming kex and good luck mate
Edit: Just read Willo's post and totally agree. I was advised just to go and take from it what I could. In hindsight I wish I had trained with GUE divers prior to the course to get more a feel for the skills and team work etc!