Do these assemblies come with new wheel studs, or do I reuse my old ones?

The studs are integral to these assemblies — they're factory-pressed in. You won't need to buy or install separate studs; they're ready to go when the hub bolts to your knuckle.

What tools do I need to swap out the old hubs?

You'll need a socket set, a hub puller or slide hammer to remove the old assembly, and a torque wrench to spec the new one to your vehicle's service manual. The actual installation is straightforward — align and bolt down.

If one bearing fails, can I replace just the bad side, or do I need to buy another pair?

These are sold as a pair. If one bearing fails later, you can source a single replacement assembly at that time — you're not locked into buying matched sets for future repairs.