Or does the installer do that for me?
The installer does it for you.
It depends on what drivers you are installing. Many new driver updates will remove most of the old driver files but not necessarily all of them. There are some free programs that will remove the old graphics driver file remnants that can cause driver conflicts. Whenever possible I prefer to remove the old driver first and then install the new.
Absolutely. Install and Uninstall instructions available.
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