Does this tool box require drilling or permanent bed modifications?

Mounting method is not specified in the product data — test-fit the crossover on your bed rails first to confirm clearance and anchor points before committing to fasteners or adhesive.

What do I need to do to the aluminum before or after installation?

The matte black finish ships ready to mount. If you scratch it during install, touch-up is straightforward with any black spray paint or aluminum-safe marker.

If the lock breaks or I lose the key, can I replace just that part?

Lock mechanism and replacement availability aren't confirmed in the product specs — contact support with your serial number if you need parts or a spare key.