Does this bumper come with sensor or fog light cutouts?

No. This cover ships as a solid panel without pre-drilled parking sensor holes or headlight washer openings. If your vehicle requires these cutouts, you'll need to mark and cut them yourself based on your OEM bumper locations before installation.

Will this fit over my existing bumper or does it replace it?

This is a cover that mounts to your factory reinforcement bar using the OEM attachment points. Your existing bumper structure remains in place underneath — this adds the BR-S aesthetic on top of your current setup.

What should I do to prepare this for painting?

Sand the surface with appropriate grit to scuff it, then wipe clean. Apply any epoxy primer or your preferred base coat system, then your final color. Reference your paint supplier's prep guidelines for the specific system you're using.