Can I reuse this gasket if I pull my header off later?

Aluminum gaskets are designed for one installation cycle. Once you torque the header down, the gasket compresses and seals. If you pull the header again, replace with a fresh gasket to maintain the seal and avoid exhaust leaks.

Do I need gasket sealer or dressing on this?

It comes pre-sealed, so you don't need to brush anything on before bolting down. Just slide it onto the header studs and torque per your service manual specs.

What hardware do I need to bolt the header down?

This gasket only — studs and fasteners are on your header and engine block. Grab the correct bolt size and torque value from your Accord service manual to finish the job right.