Do these mount at the factory rocker points or do I need to drill?

These mount at factory attachment points — no drilling. Your existing C10 holes line up with the new housings.

Are bulbs included, or do I need to source those separately?

Bulbs are not included with this set. You'll need to source H4 or equivalent based on your truck's original bulb type — verify your owner's manual or compare the old unit before ordering replacements.

Do these housings come pre-sealed against moisture, or will I need to re-seal after install?

Housing assembly condition is not specified — test-fit first and inspect the seal. If there's any visible gap or cracking after mounting, apply clear silicone sealant around the perimeter before final tightening.