Good luck!
It's a little late, but I would do a dry run at home including setting up the same way to will at the competition. This helps make sure that you have everything that you need.
As far as how much meat, is it a one time turn in to the judges? If so, then it sounds like you need to turn in a minimum of 5 ribs. I would turn in 6 just in case you don't cut through a couple bones all the way and one judge ends up with two. Do you know how the ribs are turned in? Styrofoam container, plate? I would fill the turn in container/plate with meat since a full box/plate looks better.
For a typical KCBS competition I cook 4 racks to make sure that I have enough for turn in. Each rack cooks differently and I want enough to have choices for turn in.