according to my manual after a pan revomal and filter replacement 6.5 quarts are needed for refill. After complete overhaul 11 quarts are needed for refill.
you can either drain it from the pan again but thats messy and time consuming, what ive done before is used a pump and tube setup you attach to a electric drill. Stick the tube down the refill pipe and pump out the excess. A brake bleeder pump would also work. Both of these tools can be found at the auto parts store.
as for saving the excess fluid, remember when you do a pan&filter job, youre only flushing out a portion of the total amount of transmission fluid, so you might as well discard it so you can put fresh fluid in it in the future.
i would recommend not driving around overfilled, it will cause bubbles to form.
1999-2007: ___1988 Bonneville LE LN3 (Vin C) @ 273,000 miles
and still going strong (<-Faded sun fried grayish ie needs paint)
2007-Present: ___1993 Bonneville SE L27 @ 210,000
Speeding around So Cal (<-Beautiful Forest Green)
Mods: Sylvania Silver Star headlamps. Remote start system with pageing device. K&N air filter. Tranny Cooler. High-flow cat with Magnaflow muffler. Full Class II hitch setup.