restricted driver manager can be installed by typing the command sudo sh -c "update-alternatives --install /etc/alternatives/xorg-driver-fglrx 8 auto && apt-get install fglrx-updates fglrx" as root. this will install the fglrx-updates package, and also update the alternatives link if needed.
a really nice and easy way to get it back, is using the shell command sudo rm /etc/x11/xorg.conf and reboot the system. this command will remove all files with a xorg.conf extension in the current directory.
you can get there by using the following command ls /etc/x11/xorg.conf.d and then copy the /usr/lib/xorg/modules/drivers/ folder to a new folder and rename it to /etc/x11/xorg.d. the location of the new config file is /etc/x11/xorg.conf.