Believe it or not....the easiest way to replace that seal on this vehicle
is to completely remove the front diff assembly.  If you have never
done this before, I would do that, then remove the right side
extension tube and then remove your right side axle.  If you
attempt to simply remove the long axle, there is a washer inside
the tube that can go sideways...you can re-install the long axle,
but your will not be able to shift in 4x4 if that washer is not in
the correct position.  Removing the extension tube and
re-assembling it correctly will make sure the washer stays
in it's correct position.  The only way to make sure the washer
stays in place is to apply voltage to the actuator, it makes it's
shift which captures the washer in place, you then can remove
the long axle shaft without having to worry about the washer
moving around.  If it's the old style heated element actuator,
you must keep the voltage applied, otherwise it will back off
when the voltage is removed.  The newer style actuator will
stay in position once it's been moved "into the correct position".

On the other hand, I always just use a very long screwdriver
to reach down inside the tube, center the washer and then
re-install the long axle....but I've done literally hundreds of
these types of repairs.

Ian