Under this situation, there should not be much antifreee in transmission fluid and if the the fluids are not pink colored, you need not flush it. Replacing the fluids would be sufficient and the little antifreeze would soon evaporate.
Run the engine to warm up the transmission fluid and drain it.
Replenish the fluids and repeat until the fuids are bright red and you should be good to go.
As to the stutter, it could be someting else that is related to the engine. Check the distributor cap for presence of condensation. Check the spark plugs and wires.
Monday, January 23rd, 2012 AT 12:31 AM