Will the existing fog light cutouts work, or do I need to modify them?

Verify your current fog hole locations against the Denali bumper profile before finalizing mounting. You may need to adapt or enlarge existing openings to match the new bumper's cutout design — test-fit and measure from the core structure before committing to any drilling or grinding.

Are there sensor holes pre-cut for parking sensors or collision warning systems?

This bumper cover ships as a solid panel without pre-drilled sensor provisions. If your vehicle has OEM sensors mounted in the bumper area, reference your vehicle's OEM bumper hole locations and mark those positions on the new cover before final installation. Drilling should be done carefully from the rear side to avoid surface damage on the visible face.

Can I install this on a lower valance or does the stock valance need to come off first?

The lower valance and this bumper cover are separate components. Your existing lower valance can remain in place — the bumper cover mounts independently to the frame mounting points. Confirm that both pieces have adequate clearance from each other and that paint prep is done on any areas where they meet or overlap.