Do I need to resurface my header and head before installing this?

Check both surfaces with a straightedge. If they're flat and clean, you're ready to bolt down. Any warping or pitting reduces sealing—have them surfaced at a machine shop if needed.

What fastener torque should I use when installing?

Refer to your vehicle's service manual for the correct spec. Over-tightening aluminum heads can crack them; under-tightening causes leaks. Get it right the first time.

Will this gasket work if my header is used?

A used header can work if the sealing surfaces are still flat. If it's warped, dented, or pitted, a new gasket won't save the leak. Inspect the header condition before ordering.