As far as a diet, I always tell people to find a diet they can live with for the rest of their lives. If you can't do that diet forever, don't bother starting because you'll eventually give up. I personally have followed a low-carb diet for 9 years now and feel amazing, have fantastic blood work, etc.  It does work and is healthy for most people, despite what nay-sayers and "experts" want the public to believe. It's especially helpful if you have metabolic syndrome. But again, what diet you choose needs to be something you can live with. If you give something a real try (meaning more than a couple of weeks) and it's not for you, I'd suggest moving to something else. Just beware the diets recommend nothing but juice or soup, etc. Those generally don't work in the long haul.

As for exercise, I'd say it depends on your disability. I'd recommend starting with something easy - maybe walking if you can, and work your way up to other activities as you are able. The key for most people is finding an activity you love to do. And don't just think of exercise as pumping iron on running on the treadmill. Bowling, tennis,.. playing the Wii... it's all good as long as you are moving. :)