I have to confess, I have no idea what those commands were doing but I am pleased to report that it all worked. After rebooting, the NVIDIA settings application was present and I now have 3D settings for Desktop Effects. In time, I'll try to work out what it is you have told me to do, but for the moment, I am just excited that it worked.
Thank you for your help. I could have spent weeks trying to work out a solution.