Oh, jeez. just get on the mat and don't worry; you are not signing away your life and you will either like it or you won't, either take to it or not. And if in a wk or a month or a yr or a decade, you decide "nope, not for me" that's ok too.
James we have a little motto that says alot in our dojo. "JUST DO IT". Look how well it did for Nike
. Anyhow get in there and go and most important have fun with it. Good Luck.