Will this manifold fit my current turbo setup?

T4 flange standard means it bolts to any T4 turbo. If you're running a different flange type (T3, T6, etc.), you'll need an adapter or a different manifold.

Do I need to prep or paint this before installation?

Stainless steel won't rust, so paint is optional. If you want color match, light surface prep and high-temp paint work fine. As-delivered, it's ready to bolt up.

What fasteners should I use to mount this?

Mounting hardware is not included with this manifold. Use stainless steel bolts rated for your engine's head bolt pattern—refer to your engine builder or service manual for torque specs and hardware size.