Do I need bulbs for this headlight?

Bulbs are not included with this assembly. You'll transfer your existing bulbs from your current headlight or source new ones separately — the housing accepts standard automotive headlight bulbs.

Will this mount straight to my truck without any modification?

Yes. This assembly mounts at the factory headlight points with no drilling or bracket work needed. Just disconnect your old headlight, unbolt it, and bolt this one in its place.

What if I only need one side — do I have to buy both left and right?

You can buy left and right separately. This listing is for the left (driver) side only. Order the right-side assembly separately if you want to replace both.