Do these mount at the factory fog light holes?

Yes—these use factory mounting points. No drilling or bracket fabrication needed. Test-fit before final fastening to confirm alignment with your bumper opening.

Does the switch come with wiring harness?

The switch is included, but confirm the harness routing with your vehicle's wiring diagram before committing to a mounting location. Some buyers run it along the steering column; others go through the dash.

Can I replace just the bulb later?

H11 bulbs are a standard size and widely available. You can swap them out as maintenance. Make sure the engine is cool before removing the lens.