Will this work with my existing wheel speed sensor or does it need a new one?

The sensor is already integrated into this assembly, so you're not hunting down a separate part. If your old sensor was damaged or worn, this replaces the whole situation at once.

Do I need a special tool or press to install this?

You'll need standard socket and wrench work to remove the old hub and bolt this one in place. A press or bearing puller is not required since the bearings come pre-installed.

What if the hub doesn't fit my rotor or caliper bracket?

This is designed as a direct replacement for the factory configuration. If fitment is tight or misaligned, stop and verify you have the correct assembly before forcing any bolts or brackets.