Uninstall the old driver with Driver cleaner Pro.
Driver Cleaner Professional download from Guru3D.com
This step can vary before or after yo do that. Get the new drivers. Restart then install the new drivers. restart again to get the new driver fully functional.
If you do it any other way the new drivers will not install and work properly. Just uninstalling the old driver and then installing the new ones right away will confuse the system without a restart. Possibly even make it so that the new drivers dont isntall and function properly.
It stinks having to restart twice but it is the best way to go about a driver change.