If you have other transmissions around and let's say you broke this one beyond repair, I say, oh well. Learning what not to do is, in my opinion, sometimes just as important as learning what to do. If it is irretrievably broken or you just don't feel like you have the expertise to try and correct the issue, just let it be a mistake and move on. You know how to replace the neutral drain components, and that's what most often wears out in these transmissions. And John gave a good tip if you absolutely must change the oil. It'll be all right.
That is exactly what I did. I just chalked it up as a teachable moment. I do have spare transmissions, so I'm not too upset. I do appreciate your input though.