Has he had a vet check? If not, I'd recommend it since he probably hasn't seen one in at least two years.
Like Northern said, get the farrier out there as fast as possible to fix his feet, poor guy.
Is he skiddish with you, or does he do pretty well? Does he let you halter, brush, and generally do groundwork around him? If he's able to do that, it's just a matter of getting him used to humans again. Sit outside his stall and spend time with him. Read to him, talk to him, or sing to him. Get him used to your voice and your presence.
One other question...is his coat curly looking? This could be a totally unfounded concern, but not shedding and a curly coat are signs of Cushings....
"Sit tall in the saddle, hold your head up high. Keep your eyes fixed where the trail meets the sky. And live like you ain't afraid to die...don't be scared, jut enjoy the ride." - Chris LeDoux