Do these mount at the factory fog light points?

Yes. These are designed to use the factory mounting locations with the hardware provided. No drilling or cutting required.

Does the switch need to be wired into the existing dashboard harness?

The switch connects to the included wiring harness. Tap into your factory fog light circuit or route the harness to a clean power source and ground — your service manual will show the best approach for your Pilot.

Are the lenses sealed or do they need resealing after install?

The lens seals are pre-assembled at the factory. Check the fit once installed — if water intrusion occurs later, resealing may be needed, but these should be watertight out of the box.