Hi there,
The transmission is not supposed to be serviced before 100K miles. You are not overdue.
However, it is good preventive maintenance to drop the pan, replace the filter and refill with 8 qts of Dexron III. I would not bother with flush.
I did mine at 30Kmiles and the fluid was dirty. If you wait until 100K, you may be too late. Do you still have factory warranty? I had the six year, 100,000 mile expire in January and it is still going strong at 46K.
It may be a good idea to flush the brakes at the same time.
W115nut