I want to complete a marathon before I die

That's pretty much it. Except I keep breaking. Tore a couple of muscles a few years ago, with IT band tendonitis and hip bursitis just to add to the pain. Currently I've got a couple a herniated lumbar disks, spinal nerve compression causing pain and numbness down one leg making walking difficult. But dammit, I'm at least walking 1/2 hr/day in addition to PT (again).