If you have transmission fluid leaking out of the side of the trans at the selector shaft, this is the culprit.

You remove the shift lever with the ball attached. You will find it easier to remove the shaft than to try to replace the seal with the shaft in the trans. To pop the shaft out, you put the transmission in neutral, remove the small housing that holds the reverse light switch and the shaft will slide out. Replace seal slide shaft back in and put a light coat of sealant on the reverse light switch housing and you are good to go. Reinstall lever. We now also have the new o-ring for the reverse light switch housing.

Someone shared with us some more detailed instructions that I have added here. Yes it can be done instead, remove the whole reverse switch cover, 3 x 11mm M7bolts, be aware spring pressure and there's a metal cup on top of a circlip on the shaft that may be displaced and fall out; remove the ball arm from the right side and then ensure that in neutral and you will be able to push the shaft through the box, when the threaded end is almost at the seal it will probably feel stuck, a gentle tap may be required.