Do I need to remove the bumper to install these?

Yes. Access to the mounting points inside the bumper cavity is required. You'll need to unbolt the front bumper, secure the fog lights to factory points, reconnect the switch harness, and reinstall. Plan 1–2 hours if you're moving at a relaxed pace.

Will these plug into the existing wiring, or do I need to run new wires?

These come with a harness and integrated switch designed for OEM mounting locations. Confirm the connector type matches your vehicle's factory fog light port before committing—if it doesn't, you'll need to splice or use an adapter.

Can I replace just the bulb later, or are these a sealed unit?

The 881 bulb is replaceable. You can access it from inside the assembly without removing the entire light. Replacement bulbs are cheap and widely available.