Welcome to the site, there is a lot of good information right here in the stickies in this forum. Ill help you out.
Care sheet
http://ball-pythons.net/forums/showt...thon-CARESHEET
FAQ's
http://ball-pythons.net/forums/showt...Husbandry-FAQs
Glass Tank setup
http://ball-pythons.net/forums/showt...p-w-pics-*DUW*
Tub setup
http://ball-pythons.net/forums/showt...e-Basics-*DUW*
As for getting a BP at an expo, that is a great idea. As for getting the tank and everything then, I think not such a good idea. You should have all your supplies before hand, and your tank or tub setup and ready to go so you can trouble shoot any issues. That way you bring your bp home to the proper conditions and hes not sitting in a bag or deli cup while you try to figure out how to set everything up and he does't come into any harm if something does not function as you thought it would.