Will this molding fit if I've already modified my bumper?

This piece mounts at factory attachment points, so if your bumper sits in the original position, you're good. If you've cut or repositioned the bumper, test-fit first before assuming bolt-down spots align.

Do I need to prep this before painting?

Standard paint prep applies—light sanding, primer, and topcoat. The molding arrives ready for finishing, so approach it like any other body panel going into your booth.

Is this just the trim piece, or does it come with bumper hardware?

This is the molding only. Hardware like clips or fasteners you'll source separately or verify against your specific bumper assembly before ordering.