Do I need a bulb for this headlight, or is one included?

Bulb is not included. You'll transfer your existing bulb from the old headlight or source a replacement separately — both H13 type bulbs are widely available at any parts store.

Will this bolt directly to my vehicle, or do I need to modify the mounting?

Bolts straight in at factory mounting points — no drilling, cutting, or bracket fabrication required. Hand tools and about 15 minutes are all you need.

Does this come with the wiring harness connector, or do I reuse the old one?

Reuse your existing connector from the original headlight — the assembly is designed for direct plug compatibility with your Explorer's harness.