Easiest way: unplug the old one, plug in the new one, install, plug in the old one, boot the new one, move files over, unplug the new one, reformat the old one, plug in the new one, done. That ensures you don’t accidentally wipe the wrong drive at any point.
I highly doubt that that is a self-encrypting drive so no it doesn’t do its own encryption. But even if it is and does, it doesn’t mean anything to you because it will automatically unlock regardless of who’s using it unless you set a separate password and unlock it every boot.