no, he needs to CLOSE the X server.
what ya do is press ctrl+alt+f1 then login as root and type telinit 3.
then when the messages stop press enter and youll see that your prompt is back. then run the nvidia setup. once its done, type telinit 5 and X will pop up. then go back to ctrl+alt+f1, type exit to logout and then ctrl+alt+f7 to get to X. youll know that the driver setup is successful if, when X starts, you see it flash a few times and show the nVidia logo.