I'm assuming you're doing the front axle as those tend to wear out quicker. Did mine recently, basically followed the procedure in the factory service manual.
First jack up the front end, remove wheels, calipers and rotors. Then remove front driveshaft, then check that the pinion rotates smoothly. Using an inch-pound torque wrench, record the torque required to rotate the front pinion. Then remove the pinion nut, preferable to use a spanner and a breaker bar, but some people use an impact hammer (air ratchet, whichever you prefer), it's just harder on the gears and bearings. Remove flange, you may need to use a puller. Then you can get at the seal, you should be able to get it out with a hammer and chisel, just don't go crazy.. you can destroy the old seal but don't damage the housing. Install new seal, reinstall companion flange. Tighten pinion nut, then use a torque wrench to rotate the pinion gear - rotating torque should be equal to what you recorded during removal plus 5 inch-pounds. If it's less than what you need, tighten the pinion nut a little more, then check again. Once you've got that sorted, reinstall front driveshaft, brakes, wheels and you're on your way. Hope this helps!