Wow, that's a first.
Yes, I'm sorry.
Since changing gear
oil isn't a 3000 mile interval thing, I'd just stick a little vacuum pump in the fill hole and suck it all out. Pulling a trans to drill and tap a hole would be a big undertaking and as anal as I am, I'd be worried sick about leaving shavings in the case.
It's been awhile since I've built a Toploader, but I don't think removing a tailhousing bolt will let it drain, but you could try.