[Big-Foot]

The sealing surface is on the pinion yoke - which you will have removed to gain access to the seal. They can be tough - I just typically pry them out with a large screw-driver. You won't hurt anything. The front bearing is back in there a ways - just be cognizant of its presense.

When you re-install the new seal make sure that you lubricate the sealing surface with a dab of grease. Then you will want to make sure that the splines are clean on the pinion shaft and that the yoke is also very clean. Put a little RTV on the splines of the yoke and re-install making sure that you install the yoke in the same location it was originally installed and that the nut is turned no tighter (mark it's location) than it was originally. That way you will get the proper preload on the pinion gears. If you have already removed the yoke / nut without marking them, you will need to sneak-up on the torque until you have removed all of the slack in the bearings, but have not excessively pre-loaded the bearings. There are some rules of thumb in regard to how many inch-pounds of torque it should take to rotate the pinion, but I have found very little consistency in these rules. I just take all the slack out of the bearings and use red loc-tite on the nut.