Do these bolt directly to the factory fog light location?

Yes—these are designed for the OEM mounting points. No drilling or bracket fabrication needed. Standard hand tools and basic fasteners get the job done.

Is the switch plug-and-play or does it need custom wiring?

The switch comes with a wiring harness, but connection method to your vehicle's electrical system will depend on your comfort level with in-dash work. If you're experienced with car wiring, it's straightforward. If not, an installer can complete it quickly.

Can I use the OEM bulbs that came with my car, or do I need new ones?

These assemblies accept standard automotive fog light bulbs. If you already have bulbs in your vehicle's fog cavities, test them first. Otherwise, pick up compatible H3 or H11 bulbs (check your manual for the correct type) at any parts store.