How do you change transmission oil on 1990 Oldsmobile regency?

To change the transmission oil on a 1990 Oldsmobile Regency, start by warming up the vehicle to thin the fluid for easier drainage. Next, safely lift the car and place it on jack stands, then locate the transmission pan and remove the pan bolts to drain the old fluid into a suitable container. Replace the transmission filter if necessary, clean the pan, and reinstall it with a new gasket. Finally, refill the transmission with new fluid through the dipstick tube, checking the level as you go.