Changing an automatic transmission filter is possibly the messiest routine maintenance a person can do on their 4x4. We recently dropped the pan and did this on our daily-driver F-150 and with a little ingenuity kept from wearing most of the transmission fluid like normal. It seems simple enough, but we never thought before to use a transfer-pump, this one is $8 at Harbor Freight (and this months issue of 4WOR has a 20% off coupon), to pump the fluid out of the pan through the dipstick tube so it wouldn't drop on our head.
We used the transfer-pump and pumped about three quarts of fluid out of the transmission pan through the dipstick tube into a bucket propped precariously on the front bumper.
Even with getting three quarts out with the pump the pan still had about 2-2.5 quarts in it. That much was enough to not slosh over the edge and onto us and the ground when it was lowered off the truck. Like normal humans we did this in the driveway on our backs, no fancy lift or shop here!
Things were going well until we pulled the old filter off of the valve body. It dumped about another half a quart onto the ground, thankfully we had cardboard on the ground. We keep old shipping boxes around for this very reason.
Of course the valve body keeps dripping, onto the ground, while we work quickly to get the new filter on and pan back in place. Another reason this is such a messy task.
Finally we were able to refill the transmission with brand new fluid. We choose Amsoil for this task because it's fully synthetic, handles heat better, and lasts longer than traditional ATF.