Hi Stephanie,
You are at about the same weight I was when I started (289). To be honest, I couldn't even think about Cathe at that time. I started out with one of those Tony Little-style (I know--ahhhh!) glider thingys because it's no impact on the joints. When I got strong enough, I started riding my bike. I'm talking major celebration when I rode an entire mile. (I ride 30 or 40 regularly, now--daily in the summertime). Then, when I got stronger from all the bike riding (about a year or a little more), I started lifting weights. It was all I could do to get through a 20-minute segment of Lift Weight to Lose Weight with Kathy Smith--with no weights. I can do Cathe, now, at the weights she uses and have almost all of her newer tapes. Currently, I'm still trying to conquer IMAX before I move on to IMAX II. I just can't do that last interval--but I will!!!!
The point I'm trying to make is that you may not be able to begin with Cathe. She's quite advanced. I'd hate for you to get discouraged before you get started. Even walking the six blocks to the corner grocery store and back were daunting when I first got started. Don't get me wrong, there are people who start with Cathe. I think Donna is one (getnfit@39). She could probably tell you a lot more about it. But don't give up, no matter what you do. It's a long road, but it IS possible. I've been at it three years now. A little at a time, but the gains you make will seem big to you. You'll feel better and you'll look better.
Good luck