Okay Crossfitters - need your advice, words of wisdom, etc.

I've been doing some WODs at home, but nothing like the full Crossfit workouts they post on the website for my local box (mostly due to lack of equipment). My WODs tend to involve 10 lb. dumbells, a 20 lb. kettlebell, body weight and a small step up. (Sometimes I'll also do yoga, pilates or dance based workouts with DVDs).

I had been waiting on getting my annual health benefit from work to be able to afford the dues at the local box for just a few months. I can only afford 4 months worth with the health benefit, so I probably won't continue my membership after that unless I can work some sort of sponsorship or barter out with the owners, still I have really wanted to try it all the same. Because of that I want to get the most out of my 4 months as possible. Now that I have my check, I have my assessment/intro session all signed up for the first weekend in February. So these are my questions for you -

What should I expect?
Any tips or tricks or advice for a newbie?
What was your own experience as a newbie? (Esp. if you, like me, are going in not already in great shape)
What, if anything, can I do at home over the next couple weeks to best prepare for getting started in a box?

Thanks for the input!