Do I need to replace both sides or can I do one hub at a time?

You can replace one hub if only one side is worn, but bearings wear in pairs. If one is bad enough to swap, the other is usually not far behind. Plan on both to avoid a second teardown soon.

Will this work with my existing brake rotor and caliper?

This assembly is designed to work with factory brake components. Your current rotor and caliper bolt straight on. Inspect rotor thickness before install — if it's near the wear limit, replace it at the same time to avoid noise and pulsation.

What tools do I need to install this?

Basic socket set, breaker bar, and jack with stands. You'll also need a torque wrench — refer to your vehicle's service manual for factory torque specs on the axle nut and mounting bolts. Do not guess on these values.