Someone on the more specific Horse forums may be of more help. Myself I've seen them with a fair amount of play. If the wear seems even, I personally would keep it as is as the two gears are used to playing together for this long.

Thanks, Tomplum. I took your advice about the ring gear. I took a close look at the worm and it showed a little wear on it also. It would probably wear the ring gear teeth down to match it anyway. I did find some good seal drivers on the cheap. a piece of 1 1/2" PVC works good for the tine shaft seals and a piece of 1 1/4" PVC works good for the front tine drive seal.
Like I do a lot at my age, I forgot to order the gaskets so will have to wait for them 'til I can stir up some dirt.
Mike