Calm down! It'll be okay! You can borrow stuff from other people for grooming if you forget something - we usually forget at least one thing every year (it's usually scissors).
We have a toolbox with everything in it.
This includes:
Newspaper if they will be there overnight so the paper on the tables doesn't get disgusting, and also to put on the floor underneath you while you're grooming to collect at least some of the loose hair (we always forget the second part)
Water bottles and feeders (plus food and water)
Hay
Grooming combs
Scissors (to trim their tails)
Lint rollers (to get the dead hair off and clean ourselves off)
Pens
Pedigree info
I think that's it...
As for dusting, most people dust for a week up until a few days before the show. Dusting closer to the show for whites, beiges, and other lighter colored animals, and pulling dust earlier for darker animals.
For example:
With my standards, I will be dusting them everyday from Wednesday, March 16 to Wednesday, March 23. My pink white, I'll dust until Thursday. Now, if the weather is going to be extra wet on the trip up, I might dust all the standards thursday night before we leave as well.