Well, here's an update. Last night my wife happens to mention, "Oh by the way, the van is driving wierd. Sometimes when I step on the gas it doesn't go like it's in neutral or something." Damn. So I made an appointment to have the shop take a look tomorrow and let me know what's going on. I'll let you know what happens.
I'm hoping that even though the dipstick now reads OK that it really is low and wasn't originally overfilled but was filled correctly (which would make sense because it was fine before and has lost quite a bit of fluid), and that there will be a simple fix for the leak, fill her back up, and no further damage done.
Funny you should mention $700, as my first thought was, "No matter what this is, it's going to cost me $700 to fix." I'm praying it's not the full $2500 repair that most GC transmissions seem to require.
And all this because I messed around where I shouldn't have been. I'm an idiot.