I reinstalled the driver because it was the most expedient way to go about it. The name, "nvidia-346" seems to refer to the names that the repositories give to the drivers. The repositories don't work for the latest proprietary drivers. I'm not sure whether I could enter "NVIDIA-Linux-*-346.72.run" rather than "nvidia-346".
For future reference for anyone who happens to read this, the easiest way to install the latest driver is to download it from the Nvidia site. From there, you hit Ctrl+Alt+F1. Log in, then enter "sudo service lightdm stop". Then "cd ~/Downloads" (or wherever else you put the file). Next the commands are as follows: "sudo chmod +x NVIDIA-Linux--(version, in my case 346.72).run && sudo sh NVIDIA-Linux--(version).run". From there it's basically "yes, yes, yes". The uninstall command is "sudo sh NVIDIA-Linux-*-(version).run --uninstall". It worked for me to say "yes" when it asked me to restore the previous xorg configuration and continue to uninstall normally. Next, I entered the same install sequence of commands that I had originally entered and I was good to go. (Apologies for my lack of knowledge of the appropriate ways to post this stuff. This answer is by an idiot, for idiots :) To summarize: Do the update, uninstall the driver, then proceed with the normal installation commands for said driver. Steam will work, everything will be updated, and life will be good. Cheers.
Edit: For some reason, the asterisk isn't appearing in parts of my final post. The name of the file I downloaded is "NVIDIA-Linux-(asterisk)-346.72.run".