Re: Overscan and HDMI audio questions
I am pretty sure you can use a newer driver package to uninstall an older driver, just try to use similar driver versions to ensure complete removal of the currently installed driver.
Example: Do not use 260.19.44 to uninstall 270.xx drivers, they are likely different enough to cause potential issues when uninstalling.
Yes the PPA is added to your repositories in synaptic and you use synaptic to install files from that PPA. The upgrade manager will automatically recognize when there are updates and ask you if you want to install the updated driver.