Do I need to wire this directly to the battery, or does it tie into an existing thermostat switch?

Wiring configuration is not specified in the product data. Before installing, confirm whether your vehicle uses a factory thermostat switch or requires a standalone relay and switch kit for operation.

Will this fit in my stock radiator shroud, or do I need to modify the opening?

The 12-inch diameter is a common OEM size, but shroud fitment depends on your vehicle's cooling system design. Verify clearance between the fan blades and shroud before final mounting.

Does this come with mounting brackets and hardware?

The assembly ships as a fan unit. Brackets and fasteners are not confirmed—source these separately or verify they're included upon arrival before beginning installation.