Make sure you don't go over 150 internal temp on that Pork Loin before you pull it and make sure you wrap it and let it rest at least 30 minutes before you slice it for judging. If you're cooking between 225-250 it shouldn't take more than 3-4 hours to cook it.
If you make your own sauces and rubs, see if they've got a contest for it and enter your own stuff. Never know, you might win it.
Take a camera with you and take pics of your turn-in stuff. Not just to show us back here but to keep for your own. If you do real good in a category, you don't want to have to try and remember how you dressed up your box. Consequently, if you do bad in a category, you want to be able to see what didn't work.
I'm planning on attending a KCBS event here locally in Sept. I've looked all over for Checklists and the sort and here's what I finally came up with. About a month before the event, I'm going to camp out in the backyard and have everything with me that I'm planning on taking to the event. I think that will be the best way to prep for this thing. Sounds like you're kinda close on time though. It would sure be a good way to figure out what you'll need though. But being just 6 miles from home and having someone there to make a run back to the house should help in case you forget something. Here's one of the checklists I found: http://www.novia.net/~cedmunds/gobs/chklist.htm
Also, try to find out if they're using KCBS judges or local "dignitaries/celebrities". I remember a non-sanctioned event I cooked in one time that used local dignitaries. I cooked the same ribs that I always do and the fella right next to me cooked his and then slopped them down with what looked like French Dressing. I can't remember how many teams competed but his ribs won and I was somewhere below the middle of the pack. I figured if I ever did that competition again, I would just boil my ribs and dip them in Heinz 57 or something....heheheheheheh. They wouldn't know the difference.