Drop the pan and replace the filter and fluid yourself. Their is a drain plug in the pan so it makes it much easier. It is very important to change the filter at least once from when trans was new and breaking in. I have heard too many horror stories about pressure flushes, not for me.

Here is what I plan to do very soon to my very own since I just turned 50k:

First drain fluid with drain plug. Capture the fluid in a bucket and measure the amount of fluid you get form just the drain plug. Make note of the amount.

Next drop pan and change out filter. Install pan and refill to proper level.

Then in 100 miles or so, drain just the pan and refill with same amount.

James