Will this cover the bumper sensor holes on my truck?

This filler closes the lower valance gap. If your truck has factory sensors in that area, you'll need to cut openings or route around them during installation — test-fit first to confirm clearance.

Do I need to paint this before bolting it on?

Comes in primer-ready finish. You can install bare and paint after, or paint before mounting — either works. Just make sure fastener holes stay clear.

What fasteners hold this in place?

Uses factory mounting points, so you'll need hardware that matches your existing bumper assembly. Check your service manual or have a fastener kit on hand during install.