Oh, bring the credit card for sure. There will be so much that you'll want and HAVE to have that you'll need it along.
I hope you not only learn a lot, but find something that you LOVE. From my experience, a good fitting includes measuring your body all over, then plugging those numbers into a magical formula that gives you a "cockpit" measurement and lots of other confusing things. I've bought 5 bikes new and all my fittings were detailed and took a couple hours to get just right. I make my LBS work for it.

Have fun and be sure to report back on Saturday so we can hear all about your experience.