Do I need to run new wiring, or does this use existing harnesses?

The switch taps into your vehicle's electrical system at the factory switch location. Exact wiring routing depends on your Altima's setup — have a shop or experienced builder verify the connection points before powering on to confirm compatibility with your specific year.

Are the bulbs included, or do I need to source them separately?

Bulbs are not included with this assembly. You'll need to purchase the appropriate fog light bulbs separately and install them into the housings.

Will these fit without any modification to the bumper or fascia?

These mount at the factory fog light locations using existing mounting points. No drilling or bumper modification is needed, but test-fit before final installation to confirm panel alignment on your specific vehicle.