Ok, i'm not well versed in the Nvidia driver update process, but plenty of people are here (especially due to this lol), so hopefully someone can give you some more clear instructions on that bit. There is this post about the installation and purge of old drivers that you can look at here:
But possibly someone might have brand new instructions for you. I'm not sure if the reinstall of the desktop is necessary at all, but like I said, I'm not well versed in the Nvidia driver install and removal process.