Will this guard fit with my existing front bumper?

Yes — this guard mounts at the factory grille opening points and works with OEM bumpers. Test-fit before final tightening to confirm clearance with any custom additions you've installed.

What fasteners do I need to secure it?

Fasteners are not included. Mounting method not specified — you'll likely need bolts or brackets to attach at the factory points. Check your vehicle's service manual or consult a technician for the correct size and torque specs.

Does stainless steel need paint or primer?

Stainless steel doesn't require paint and won't rust bare. It will patina over time with road exposure, which is normal. Wash it regularly to keep it looking polished, or have it powder-coated if you want a specific color match.