Wow! Good luck!
A couple years ago we were camping in Southern Missouri and the neighbor camper was a woman and a man in a wheel chair. The man came and went from the motor home quite a bit, but he always got in and out by sitting down on the steps and sliding up one step at a time on his butt. If the feet are incapacitated, I don't know of any other way to do it. I had a right knee replacement last July, but could lift with the other leg one step at a time, until the replacement knee leg strengthened. It sure wasn't fun. Hang in there through, and follow Dr's instructions, and you'll get through it! Good luck!