automatic doesn't have a dipstick. Changing the fluid is a little involved, and not easy to do if you don't have access to a lift. It can be done on jack stands, but isn't a pleasant ordeal.
The drain plug is a two piece - the inner section is where you put the tool to pump fluid UP into the transmission after draining it but taking the entire plug out. You take out the insert and put the tool in and then pump fluid in. When it starts to drain back out, put the center piece in.
But that isn't the end. Now start the car up and run it through the gears. Get it up to operating temperature. Then back under the car that is now up to operating temperature to pump more fluid up into the transmission. When it starts to drain back again - start the car up, put it in gear (so now you have hot exhaust, hot transmission, and a spinning driveshaft) and pump more fluid up until it drains back again.
Cap it off and take it for a drive. If the transmission slips on a shift or is sloppy then you didn't get enough fluid in and have to add again.
That's why you can't get it done at Jiffy Lube, and why the dealer charges so much.