If you are at least an intermediate exerciser, I don't think you need to do anything to prepare, other than your 1 RM. Of course I know you don't have to do those, but I did a lot of them, and I think it was very helpful.
I am finishing Meso 1 today, and I also thought before I started that I might not be ready, but I definitely was. I can't do nearly all the pushups that the STS crew does (I just start out on my toes and move to my knees to finish up) and I need to take longer breaks sometimes during the leg workouts. So you can make it work for you.