There's all different styles depending on two-wheel-drive / four-wheel-drive, 1500 or 2500, front or rear. Some front ones are held on with one bolt in the wheel bearing assembly. All you have to do is remove the wheel and brake rotor and caliper. Some require the bearing assembly to be partially removed to get to the bolt.

You look for metal chips and rust on the end by the tip of the magnet, and look for rust buildup under the mounting surface of the sensor that pushes it up.