Hi, Victoria! Good luck on Saturday if you can find your way through the snow.
Try thinking of the test as a practice test. Find a couple people to help you before or after practice-- someone to call out techniques and an uke to practice with. Maybe Jerry will help quiz you.
During the test, ignore everyone except your uke and sensei's voice. When I tested for 5th kyu with USAF, it was at the end of my first big seminar (probably about 40 people watching). It was a little shock to come back afterward and remember they were all there, but they were very supportive.
I'm also 5'3" if I stretch... While it seems counter-intuitive, with bigger (and for me, stronger) ukes especially, relaxing seems to work best. Try to stay calm; stick a song in your head if you need to. Once you have uke moving, keep leading uke around until the throw or pin; try not to stop.
If you start the "wrong" technique, that's okay. Finish it. Then do the "correct" technique. The important thing as I believe Mary mentioned is to move (out of the way). At least that's the type of advice that's helped me.
Don't forget to get some rest the night(s) before, eat, drink enough fluids, bend your knees, breathe, etc.