My experience with CAR is pretty limited, but I do want to say that if your trees are now five years old, you are five years ahead of a lot of other guys and have something you can work with.
If you have little or no grafting experience, you could watch a few how-to videos on YouTube, cut a couple sticks off a tree of a known variety owned by somebody you know, and graft them onto a few lower limbs you might be thinking about pruning off anyway. If the grafts take, you will gain confidence to change all the branches over to some CAR-resistant variety the next year. If the trial grafts don't take, nothing is lost.