Hey Steve,
That is GREAT news! Your Dad must be one tough customer. I thought I did well after the surgery, but your Dad is doing a lot more than I was at this point. And I was only 54 at the time.
I usually preach the "Keep Moving" sermon at the end of my threads, but your Dad could show me a thing or two. Tell me when he's ready to bicycle and I'll look him up!!
Good Luck,
Steve