Hey Archie,
I'm kind of a n00b here ( <-- see, it says it just over there to the left!) so I'm not familiar with the extent of your injuries. If you're physically capable, is some form of water aerobics a possibility? Zero impact, flotation benefits, warm water, usually has hot aerobics instructors , etc. I know a number of people who have used it as therapy and/or to recover after injuries.
Regarding diet: My personal philosophy is called "the caveman diet" - if it didn't exist 4,000 years ago, I try to not to eat it.
This basically means lots of fresh fish and chicken (always grilled, olive oil instead of butter, etc), occasional beef, fresh fruits and veggies, only whole grains (i.e. true whole grain bread, the crumbly, thick, doesn't-last 24-hours-outside-of-a-fridge because-it-has-absolutely-no-preservatives-bread). Snacks are nuts and raisins. Of course I don't stick to this 100% or I'd go out of my mind, but it's a very good guideline. Make sure your portion size is appropriate for your daily caloric expenditures and you'll be fine.