If you installed the driver using the .run from AMD/ATI before, you need to uninstall it. It doesn't "upgrade". If you've done it before, it's is pretty straight forward:
sudo amdconfig --uninstall
Reboot to the opensource driver.
sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
Download the new .run and execute it.
sudo amdconfig --initial
Make your adjustments in CCC.
By the way, if you don't know this: If you use the driver from the AMD/ATI website you should watch for kernel updates when you do your normal updates. If there are any, don't do the updates until you uninstall the driver and then reinstall it after you have done your updates. If you don't, the best you can hope for is no driver after you reboot. There is a high likelihood of a big mess in the worst case.