How can I change transmission oil ? What is required?

Dry, a little over 13qts. Try asking your question on google you'll find the trans is a hydramatic 4t40-E/4T45-E then plug that into google and get: http://gm-alero.de/89/hydra-matic-4t40-e4t45-e-mn4mn5

7-Position Quadrant: P, R, N, OD, 3, 2, 1 Case Material: Die cast aluminum CONTROL SYSTEMS: Shift Pattern: (2) Two-way on/off solenoids Shift Quality: Variable Bleed Solenoid Torque Converter Clutch: Pulse width modulated solenoid control Converter Size: 245mm (reference) (Diameter of torque converter turbine) Fluid Type: DEXIII Transmission Weight: Dry: 74.7 kg (164 lb) Wet: 85.1 kg (187.6 lb) Fluid Capacity (Approximate): Bottom Pan Removal: 7.0L (7.4 qt) Complete Overhaul: 10.0L (10.6 qt) Dry: 12.5L (13.2 qt) Pressure Taps Available: Line pressure Transfer Design: Two-Axis design, link chain assembly Assembly Sites: Windsor, Ontario, Canada APPLICATIONS Chevrolet Cavalier (MN4) Chevrolet Malibu (MN4) Pontiac Sunfire (MN4) Pontiac Grand Am (MN4/MN5) Oldsmobile Alero (MN4/MN5) Saturn L-Series (MN4/MN5)