Autocross is $30 and we are the Gateway drag lot near the Wallace Bothers Grand Stand.
PDXs have two prices (Jan correct me if things have changed). We do the all day weekend sessions for $250. And the Wednesday weekday sessions go from about 3 'til dark for $150. In either case you will drive until you are exhausted or out of gas or both. I have driven both a C6 Corvette and a Shelby GT in both places and it is a blast! I slept well those nights because I was exhausted.
As far as your Vette, in both venues we have some great Vette people. Some of the best around. They will help you a lot especially at AX events. Ask them to ride with you and you with them to learn all you can (for free!). Carla, Chuck, Mike, Jeff, Bruce and others. Ask for them and introduce yourself. They were the crew I originally hooked up with when I started AXing two years ago. Then I switched to Ford and now they won't talk to me! 
Did you check out stlpdx.com? Go there and check things out to make sure your helmet is current for PDX and for other info. Have fun! Looks like you have the car for it!
Dr. Kyle Langley (and his alter ego Champ Winner)
2009 National Tour Eastern States Champion - FS
2009 SPS/R&S Midwest Division Champion - FS
2008/2009 STL Region Champion - FS
2008 STL Region Solo Rookie of the Year