Like Hartlover suggested, I too strongly recommend you dont start off with P90x.
I have Turbo Jam that I will use after I complete Chalean Extreme (I have 2 weeks left) - but I've done a couple of workouts, and they are DEFINITELY doable.
Some days will be harder than others, but just keep going. Don't think of it is as too hard; if you think of it that way, it will be. Be positive, tell yourself that you HAVE to do it, and I'm sure you will see great results. If you need to pause the videos because you're out of breath the first few times, fine. Just keep doing them! You will be amazed at your stamina after a while
Good luck!