First step in removing the pinion is taking off the front yoke. You’ll need an impact gun of some sort to remove the nut holding the yoke on, then a puller to get it off the pinion gear shaft. Once removed, a few taps with a hammer will free the pinion gear for removal from the other side. Be sure to save the shim on the yoke end of the pinion gear. This will give you a baseline for what shims to use when setting up the new gears.