hehe glad you enjoyed it!
I know what you mean. My friend would bounce around her living room as if it was nothing and I might as well of been attempting to run a marathon.
I wouldn't worry about not knowing all the moves and missing a step here and there. If I didn't know what to do, I just did something to keep moving. But don't be afraid to ask the instructor to show you something slowed down before/after a class if it's just not clicking.
Plus, when you do start to figure out the moves you are in danger of breaking out into jazzercise randomly when you hear the song outside of the class.
If I hear 'Black Betty' or Madonna's 'I'm Sorry' I'm doing the steps in my head.
Have fun! I'm jealous. I've just joined and gym and made friends w/ the boring old treadmill.