As far as a diet plan, I highly recommend The Whole30. It is a 30 day challenge with a paleo-centric focus, and is basically described as:
Cut out all the inflammatory,
insulin-spiking, calorie-dense but
nutritionally sparse food groups for a
full 30 days. Let your body heal and
recover from whatever effects those
foods may be provoking. Push the
“reset” button with your metabolism,
systemic inflammation, and the
downstream effects of the food choices
you’ve been making. Learn once and for
all how the foods you’ve been eating
are actually affecting your day to day
life, and your long term health.
Not only will it allow your body time to heal, but will also cause your body to drop excess fat quickly. I've done this myself and can't express enough how amazing it makes you feel.
For a fitness plan, I recommend Mark Sisson's Primal Blueprint Fitness. It focused around 5 essential full-body movements, and is designed for beginners and advanced persons alike. It does not require any expensive equipment and is extremely effective. I have also been following this plan and love it. If you are looking to eventually get into P90X and have little experience working out then I definitely recommend starting here. P90X is hardcore and I don't know anyone who started with it as a beginner and made it all the way through.
If you want to read more about the style and affects of P90X and CrossFit (another hardcore fitness program), then I recommend this article from Mark Sisson where he goes into great detail about the benefits and possible downsides to both.
Enjoy changing your life!