Will the W221 fog lights fit directly into this bumper's cutouts?

The bumper is engineered with W221 fog light mounting points. Verify your light housings' overall diameter and flange depth against the cutout openings before final assembly. Minor trimming of the bumper surround may be needed depending on your specific light unit's fitment.

Does this bumper have sensor holes for parking aids?

This is a direct bolt-on cover with no factory sensor provisions pre-cut. If your vehicle's lower valance uses bumper-mounted sensors, reference your OEM sensor hole locations and drill accordingly before final installation to maintain functionality.

How should I prepare the surface before paint?

Sand the entire panel with appropriate grit to dull the primer surface and remove any mold release residue. Clean thoroughly, then apply your chosen epoxy primer and topcoat system. The FRP accepts standard automotive finishes well once properly prepped.