I would think the fluid in the converter drained back into the trans/leveled off causing the overfill view, which is why the trans must be running. To fill the converter and have the pump running.
With that color fluid etc, I would probably drop the pan, change fluid and filter, rotate the converter by hand to ensure it moves freely. Fill the trans with 7 quarts of trans fluid. It will probably want 3-4 more once you get it running, until then you'll have no idea and it shouldn't be an issue to run like that for 10 minutes when you get the motor up and running.
Other than that...I don't know there'* much you can do to check it over.
00 Regal GS: All kinds of cool stuff.