Will this work if my bumper fascia is slightly warped or faded?

The trim molding clips or fastens to the bumper itself — a warped fascia might affect how cleanly it sits. Test-fit first before committing to final installation. If the fascia is severely damaged, you may need bumper repair or replacement alongside this trim.

Does this include mounting hardware?

Mounting method and hardware are not specified in the product data. Check your vehicle's existing trim to see what fasteners are already in place — you'll likely reuse those. If installing on a new bumper, bring the molding with you when sourcing the fascia so fitment can be verified.

Can I paint this before installing it?

You can, but it's cleaner to install first and paint as part of the bumper. If you do paint beforehand, mask off mounting points so adhesive or fasteners can grip properly.