Turn the rotor upside on a workbench. Use paper towels or a rag to remove grease, grime, dirt and whatever, so you can get a good look and feel for where the inner bearing lives. You'll see a rubber seal encased in a metal rim. You probably will need a new seal due to possible damage removing it. Reach in feel for the far side of the bearing, once you have that in your mind turn the rotor over again so the stud side is up and place a drift (or a 6" or so socket extension) against the bearing and give the drift a rap with a hammer. Not real hard because the bearing is not pressed in, just held in place by the seal. Once you knock the bearing out, do the same thing to remove the seal. Clean the bearing in some solution to remove all the old grease. Visually look at the rollers and the cage of the bearing to satisfy yourself that you have no burned rollers, scarred rollers or other defects. If you roll the bearing cage listen for a gritty sound and gritty feel. The bearing should roll relatively smooth. To pack the bearing, use bearing grease from an auto parts store. Put a gob, maybe 2 tablespoons full in the palm of one hand. Put the bearing over a finger or two of your free hand and now what you want to do is mash the large open end of the bearing into the grease so that grease squeezes up and through the rollers and the cage. Do not simply coat the outside of the bearing assembly, the grease must be forced up through the rollers. Once you have squeezed grease through one portion rotate the bearing on your finger and continue all the way around. Not hard to do, and squeezing the grease up and thru is why it's called 'packing'. Don't put grease in the dust cap either. That would be unnecessary and messy.