When you take the driveshaft off, mark the differential-end of it so that you can put it back on in the same position (avoids vibration).
When you drive the new seal in, try and use a flat driver that covers the entire face of the seal and drive it in straight.
If you don't drain the transmission before removing the driveshaft, you will probably get some ATF pouring out the back. As long as you have a pan underneath, either way is fine.
__________________ 91 GT convertible AOD B&M shiftkit 3.27
89 LX 5.0 hatchback T5 2.73 | 
replacing rear seal on manual tranny for 94 GT... 
