Will this mount to my factory bed rails without drilling?

Yes. Clamps attach at factory rocker and rail points — no holes or fasteners needed. Hand-tighten the clamps and you're done.

Do I need to prep or paint this before installing?

No prep required. Mount straight out of the box. If you want a custom finish, sand lightly and paint after test-fitting clamps to verify proper alignment.

Can I open this cover while driving, or do I need to fully retract it first?

Full retraction is recommended before moving the vehicle. Rolling it open at speed risks wind catching the cover and putting stress on the clamps.