Do I need new hoses or can I reuse my old ones?

That depends on the condition of your existing hoses. If they're cracked, hardened, or leaking, replace them. If they're still flexible and hold pressure, you can reuse them — just make sure they fit snugly on the inlet and overflow ports of this tank.

What mounting hardware comes with this tank?

The tank assembly ships as-is. Mounting hardware isn't specified — test-fit it against your radiator shroud to see what fasteners you already have or what you'll need to source separately.

Will this bolt straight into my engine bay or do I need to drill holes?

It's designed for factory mounting points, so no drilling should be necessary. Line it up with the existing shroud attachment locations first to confirm fit before tightening anything down.