Well, things worked out. I took the old wheel up to the bike shop. I was going to hop the bus, then decided to take the car instead. Scored almost an hour and a half someone else paid for on a parking meter three doors down from the store.
That let me check a few other bike shops in the area while I waited for them to swap my cassette to the new wheel.
I ended up buying a new wheel, even managed to get a 36 spoke instead of the 32 I had. The old one's on the rack in the garage, I can always strip it for spokes if/when I need them. The rag joint went together smoothly, the wheel barely argued going back into the dropouts. I was using an axle mount kickstand, but I left it off this time and am trying a center stand. If it doesn't hold up I'll switch back.
Took it for a quick test, and it's good. Nice to have a solid wheel under me again.