Do I need any additional wiring or relays to install these?

The integrated switch handles the electronics — no external relay or standalone harness required. Run power and ground to the switch terminals and you're done.

Will these work with the factory bumper cutouts, or do I need to modify anything?

These mount directly at factory points using the OEM bezel. No cutting, drilling, or bumper modification needed.

Are the H8 bulbs a one-time purchase, or do they need replacing often?

H8 bulbs are standard and available everywhere. Expect typical halogen lifespan — when they dim, swap them out with any H8 replacement from your local parts store.