Will this shield block my radiator airflow?

No. This trim mounts above the grille opening and sits in the upper fascia area, so it doesn't restrict cooling air to your radiator. Your engine stays at normal operating temperature.

Do I need to paint this before installing it?

Not required, but recommended. It ships in raw finish and can be primed and painted to match your bumper. If you want bare protection without paint, mount it as-is—just prep the mounting surface for a clean fit.

What fasteners do I need to bolt this on?

Hardware is not included. Since this uses factory mounting points, verify your vehicle's service manual or test-fit the shield first to confirm what fasteners you already have or need to source separately.