ItWasMe,
this program is broken up in to several levels, including music only, direction only, etc etc,
however, while they do change often, they give you the time on the bottom which allows you to pause, rewind, fast forward etc as needed. Plus, when you first start P90x, trust me, you won't be going the full minute for each discipline (sometimes the sets are longer). So to begin with you should be able to keep up as far as changes rather easily. The only one that is a bit difficult is the Yoga, especially if you aren't familiar with yoga. It's hard to do the pose/stretch correctly when you can't see the screen
to begin with it could be a bit overwhelming but like I said before you won't be doing the exercise long enough to be worried about keeping up. They'll be doing 30/40/50 pullups/pushups and to begin with you'll (universal you) be doing 5/10/20 or less. It's all about pacing yourself and Tony is very clear to go at your pace and not try to keep up with them.