If you are replacing the outer bearing in the end of the axle tube it will not require you to mess with the backlash. If it is a c-clip axle you can freeze the outer race to make it go in easier. If it is a c-clip axle you will need a press to remove the old bearing from the axle shaft and press the new one on. If it is the carrier bearings you need to replace you should also not need to reset the backlash as long as you make sure the shims go back on exactly as they were removed. Same for the pinion bearings, as long as they go back in the same way you should not need to make any adjustments.