At that mileage, I would change the filter out.
That being said, the procedure at the dealer doesn't do anything but a fluid exchange. They hook up a tank with two bladders. One on top of the other. They fill the bottom bladder with new fluid, hook up to the cooler lines and start the vehicle. As the vehicle runs it puts the old fluid into the top bladder which pushes down on the bottom bladder and pushes the new fluid into the system. They use more than what the total capacity of the transmission uses so that they get a complete exchange of fluid.
The transmission does all the work. No force or anything like that. When they are done and the bottom bladder is empty, they disconnect everything and hook back up to the vehicle and then top off as needed.
If you did this and didn't change the filter then you have a dirty filter. The new fluid doesn't do anything to it. That is why it is better to change out the filter and then do the fluid exchange.
I had the dealer do my 2002 Silverado at around 10k miles from new and installed AMSOIL. I then dropped the pan and changed out the filter at around 70k miles. Here is my write-up on it.
I have done the same thing now on our 2016 suburban.
I've changed out several GM truck transmission with over 100k miles with no issues.