The rear tail housing seal is a common leak. The driveshaft is constantly moving in and out of the rear tail housing seal as the axle moves. This tends to wear on the seal and causes it to leak transmission fluid. When the driveshaft is removed, there will be fluid loss at the rear housing of the transmission. A drip pan will be needed to catch this fluid. You will need some additional transmission fluid to refill the transmission to the proper level.
Jack the vehicle up and support it with the jack stands. Put the transmission into neutral. Remove the driveshaft using the 11mm wrench. Hold the driveshaft with the screwdriver to prevent it from turning.
Place the drip pan under the tail housing of the transmission and pull the driveshaft out of the tail housing. Remove the tail housing seal with the seal puller.
Install the new seal by lining it up with the hole and gently tapping with a hammer around the circumference. Be careful not to use too much force---it could damage the seal. Tap it in until the outer edge is flush with the housing.
Install the driveshaft. As you insert the driveshaft into the transmission, rotate it slightly to align the splines. Push the driveshaft in most of the way to give the bearings on the opposite end room to be moved into position to insert into the rear yoke.
Insert the bolts in the universal joint and the rear yoke and tighten. Remove the jack stands. Start the vehicle and allow it to warm up. (Transmission fluid must be checked when the vehicle is warm, or else you will get a wrong reading). Check the level of the transmission fluid and add fluid as needed.
