I'm not sure Crossfit is recommended for rehab, but as a training gym I love the camaraderie and the collective push to keep going.
I would call crossfit "beyond rehab" though I am sure they can help you in rehab.
You can easily hurt yourself trying to do unfamiliar exercises.
If you want to do crossfit, I would make sure you start with an instructor that will take it slow. Be very cautious about randomly selecting crossfit exercises to do unsupervised. This can hurt. Personally I would get somewhat in shape on my own, then do crossfit after a few months of weights aerobic exercise and stretching.
My own recipe is run a few times a week, gym 2x a week.
Free weights and core in the gym, speed and recovery, not maxing out.
And do whatever you can balanced on a ball or one of those squishy things.
If you add a couple of swims a week, even better.