Does this include the bulb?

Assembly only — bulb is sold separately. You'll need an H4 bulb to complete the installation.

Will this bolt straight in, or do I need to modify anything?

This mounts at the factory points with no modification needed. Test-fit before sealing to confirm alignment with your specific vehicle.

What condition is this in — does it need paint or prep?

Assembly ships ready to install. If you want a custom finish, light sanding and paint prep work as with any hard panel part.