NABBA Figure is usually by height class, not by weight class. For height class check in, just wear normal clothes; you'll have to take off your shoes for the height measurement, but that's it. If this contest split Figure into weight classes, then you wear your posing bikini to weigh in. Usually, you check in and weigh in/measure height at the same time. So, if you go on Friday, you'll be able to both check in and weight in or get your height measured.
I show up to prejudging in my suit, ready to go. You never know if there will be changing rooms, so I prefer to be prepared for the worst (one of my contests in Germany had no changing rooms/pumping rooms - nothing). You'll have 3-4 hours between prejudging and finals to just kind of relax, touch up your tan, etc. I usually have a hotel room to go to and just get away for a while.
Most expediters try to keep backstage as free of people as possible; usually, they'll have 2 classes preparing to go onstage while one class is on stage. A lot of shows don't permit anyone beside competitors backstage; sometimes they permit trainers, so make sure you say your husband is your trainer. If they don't allow trainers, they will have people backstage who will oil you and help with tanning.
Most competitors pump up a little bit backstage - ie., do some high rep work with light weights. Some competitors bring bands with them to use, but most promotors have light weights, a bench or two, and mirrors backstage for your use.
NABBA promotors usually have water and fruit backstage too, but in case they don't, make sure you bring some water to rehydrate with when you're done competing.
Figure is usually near the beginning of the competition; usually they run Juniors, Masters, Grand Masters, then Figure before the Novice and Open bodybuilding classes. It doesn't always happen this way though; I judged a show last night and they placed Figure after Novice, the NJ titled bodybuilding classes, and the masters divisions.