The Choate comes as a complete kit. You won't need anything else.
The Choate blued unit is a satin blue/black so it matches most blued guns.
Installation should be easy. With most shotguns you basically unscrew the magazine cap, remove the barrel, and remove the magazine spring assembly.
Install the new Choate magazine follower (if you want it) install the barrel, install the new spring, install the extension tube on the gun, then install the barrel clamp.