I'll be honest, i'm no 9" expert, but i've changed seals in many rear ends the last few years ang for the most part its pretty easy. The 8.8 inch rear end uses c-clips and are extremely easy to remove (take out the c clips and the axle pulls out), but i believe the 9 inch uses a plate (for lack of a better term) on the end of each axle that holds the axle and bearing in place.
Basically, if i'm picturing this correctly all you need to do is....
1. Remove the wheel
2. Remove the brake drum
3. Remove the (more than likely) four nuts/bolts holding the bearing/axle retaining plate in place. You may need to remove the brake shoes to get to these bolts.
4. Remove the axle. This may or may not be easily done. Sometimes you will need a slide hammer to get the axle/bearing out of the rear end.
5. The bearing will likely need to be pressed off the rear end, which is easily done at most auto parts stores.
There are a few things that could be the problem. The seal could be the culprit, the bearing could be defective in some way, or the axle itself could be bent. If the axle is bent it will wear the seal out very quickly.
I hope that helps at least a little