Yes you are correct. The wheels will be barely moving if at all. The idea is to push the old fluid out by using the transmission pump instead of an expensive fluid exchange machine. You can leave the car in park or neutral and the pump will still run if it makes you feel safer. I can not take credit for the idea, I found it in a Mitsubishi service manual while I was working on an Outlander a few years ago. I just adopted the procedure for the Aveo. When I bough my Aveo used the fluid looked nasty. A 2 quart exchange would not have been enough for me.
I used to just change the filter and the fluid in the pan, but you only remove a small amount of fluid. For our cars this is around 2 quarts, other this can be 6 quarts. You can choose to do serial dilutions like avguy, but this procedure removes most of the fluid at one time. Lucky for us the Aveo has a drain plug as most other auto trans do not. I do have a fluid evacuation machine I use to remove the fluid from cars with out drain plugs via the dip tube, but again this only removes what is in the pan not what is in the rest of the transmission and the cooler lines. You can have the same procedure done at a dealer or trans shop if you are not comfortable with it. I was quoted $260 by my local dealer.
If you ask 10 mechanics you will get 10 different opinions. I expected some controversy. I have done quite a bit of transmission work as a shade tree mechanic. Some people feel 30k intervals are to frequent, I feel its cheap insurance, for less than $50 in parts and one hour of my time. I was taking with the owner of a very large respectable shop in my area one day and he said one of the biggest issues he has seen with cars today is fluid breakdown and contamination. People don't service their brake fluid, coolant, power steering fluid ect. These fluid don't last forever.
My goal was to give back a little to the Aveo community. I have learned a lot about our little cars from others on this forum so I though I would share some of my work.