Transmission fluid change for High Millage Chevy Lumina

Is there a problem with changing transmission fluid on a vehicle with high millage?
I have 1997 Chevy Lumina with 175,000 miles, bought it at 80,000.
I change the oil every 3000 miles. the last oil change at one of the 10 minute shops, said the trans fluid was very dark and dirty.
I have not had the trans fluid changed in a very long time
I drive over 1000 miles a week, about 200 a day, almost all of it highway.
I once heard something about transmission for high milage but i don't remember.
Thanx
Louis

I too have heard the advice about not changing very old transmission fluid. It's something about dislodging debris. Frankly, I have not heard any hard evidence to back up this assertion. If it were my car I would have no reservations about replacing the ATF and filter. You know it's bad.

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