California has a seven day waiting period so any pistol or rifle that is not a collectible antique you'll have to wait a week after the show to go pick it up. Also, to purchase a pistol you need your Basic Firearms Safety Certificate which will require you to take a class and pass a test. This runs $40 to $100 depending on who you go to.
If you have an NRA or CRPA membership or are in the military reserve, police auxilliary, or other qualifying organization that promotes proper firearms handling and safety you can skip the class and just take the test.
If you have no firearms experience I'd recommend you take the class.
A prior year's hunting license doesn't work anymore ?