First securely jack and support the car (you can leave the car in Park). Drain the transmission oil. Four quarts will come out right away, another 2 quarts will drain out if you give it time.
Use a long standard-blade screwdriver to disconnect the Oxygen Sensors from their plugs.
Remove the complete exhaust system, from the exhaust headers to, and including, the muffler. Remove the heat shield below the drive shaft – (8) bolts, 12mm.
Remove the (4) 12mm nuts from the rear side of the drive shaft-to-differential flange. NOTE: the nuts and lockwashers go on the back or rear side of the flange; the bolts go through the front, towards the rear.
Remove the (2) 14mm bolts that hold the drive shaft carrier bearing to the body and remove the drive shaft – it just pulls back and out.
Remove the (6) 14mm bolts holding the rear transmission crossmember to the body and remove the (3) 14mm nuts that hold the crossmember to the rear transmission mount.
Remove the (2) 12mm bolts that hold the exhaust hanger to the tailhousing of the transmission. Remove the single 10mm bolt holding the Speed Sensor #1 to the tailhousing and remove the Speed Sensor.
Remove the (11) 12mm bolts holding the tailshaft onto the transmission body and carefully pry the tailshaft away from the transmission body. Once removed, disconnect the single-wire connector to the Solenoid C. At this point, a shaft, a spring and a parking pawl might fall out to the ground. See picture for detail.
Take the tailshaft to a clean workbench and remove the (4) 10mm bolts -- the (2) black going through the Solenoid and valve and the (2) gold going through the valve only.
Remove Solenoid and valve and separator plate (the gold colored separator plate goes between the valve and the tailshaft housing.)
Clean away all gasket material on the separator plate, tailshaft housing and transmission body and carefully reassemble using the new gasket.
Now for some torque specs:
The bolts that hold the Solenoid and valve assembly body into place get torqued to 5.1-6.5 ft-lbs.
The (11) bolts that hold the tailshaft to the transmission body get torqued to 17-20 ft-lbs.
The 10mm bolt that holds the Speed Sensor #1 gets torqued to 4.3-5.8 ft-lbs.
The single crossmember-to-cushion bolt at the rear transmission mount gets torqued from 9-17 ft-lbs.
The other (2) nuts get torqued to 20-35 ft-lbs.
The (6) crossmember-to-body bolts get torqued to 40-61 ft-lbs.
The (2) 14mm center bearing blots get torqued to 25-33 ft-lbs.
The (4) 12mm bolts at the drive shaft get torqued to 13-20 ft-lbs.
At the engine, to the manifold, the (4) 14mm nuts on studs get torqued to 18-25 ft-lbs.
At the hanger, 18-25 ft-lbs.
Refill with 4-6 quarts of transmission oil and check for leaks.