Do I need the left bracket too, or can I run just the right?

This bracket handles the right side only. If your OEM left bracket is intact, you can replace just the right. If both are damaged, you'll want the matching left bracket for even support.

What fasteners do I need to bolt this to the frame?

Mounting hardware is not included with this bracket. Check your vehicle's service manual or inspect your existing bracket to identify the bolt size and quantity required for your year.

Does this come primed, or do I need to prep it before install?

Finish condition is not specified. Inspect upon arrival—if raw material is exposed, light scuffing and primer application before install will prevent corrosion behind the bumper cover.