For your first question: if she refuses, don't punish her. It looks bad and it will just freak her out even more! Circle her around at a steady canter and approach the jump from a good distance off, so she can get a good look at it the second time. Talk to her, especially if she feels tense. It will get her mindset on "Oh,hmm,what are you saying,oh! That was the jump I'm supposed to refuse at!" instead of "Oh golly,here it comes,here's that scary one,STOP!"
For your second question, I'm wondering the same thing. If it's a smaller show, then I think half chaps with paddock boots will be fine. Don't be afraid to ask the show co-ordinater, too.
It's a good idea to make sure she loads well before the morning of the show. If this isn't possible, allow yourself plenty of time the day of, so if she is difficult, you don't feel rushed.
Also, if you have time before the day of the show, it might be a good idea to take her to a show, as big or as small as you want, but don't show her. Just take her and ride her around the show grounds so that she gets used to the sights and sounds. That way, you don't have the stress of showing.
I hope this helps! And remember, you're doing this for fun!