Do I need to replace my turbo when I install this manifold?

No. This manifold bolts to your existing turbo. If your turbo is in good shape, keep it. If you're swapping turbos at the same time, that's a separate decision based on your power goals.

Does this manifold come with gaskets and bolts?

The manifold assembly is included. Bring new OEM gaskets and studs—the mating surfaces are critical, and fresh gaskets prevent boost leaks. Reusing old hardware invites problems.

What prep work should I do before bolting this on?

Clean the cylinder head mating surface and turbo flange thoroughly. Any carbon buildup or debris will compromise the seal. Dry-fit first if you're unsure about clearance in your engine bay.