If you are having advancing arthritis you have two issues to be concerned with and only one may be helped with the surgery. You have a process going on within your body that is attacking itself (arthritis is related to the host of auto-immune conditions), and you have the localized damage. The Tong Ren will work on both aspects of this condition and generally people with pain cases do very well and those with osteo and rheumatoid arthritis do well in the classes. The next time you go, ask around and you will most likely find someone who either has or had the same condition.
If you were going to do anything more extensive, I would simply add acupuncture treatments from Tom or any of his students. Acupuncture is very effective at treating arthritis both in the local sense of reducing pain and inflammation and slowing the damage done to the joints as well as balancing the immune system.
Personally I wouldn't go to the trouble of seeing John of God. Master Tam has visited with him and wasn't overly impressed with anything he saw. He wrote a book (now out of print) about his experiences. If you ask Tom, he may have a copy of the book available for you to look at. There was also a 20/20 special (or one of those news shows) on him last year. The only patient on the show from what I can remember that improved was someone we had seen extensively before hand - in other words, they were probably healed or at least well on their way before they even went to see him. Everyone else that was featured at marginal results at best. It's an awful lot of expense when you arguably have one of the most accomplished healers in the world right in your back yard.
I've met a number of other healers, gifted practitioners, etc. from around the world, and Tom and his system of healing is one of the best systems I have ever used. The results are explainable within the theory, reproducible by large numbers of practitioners outside of Tom, and generally quick.
I would simply go to a class once or twice a week and possibly add in some acupuncture treatments. Then as the time for the surgery nears, if you are feeling markedly better you could simply ask to be re-evaluated.