Better to uninstall the no-view I mean nouveau driver. I have the same video card and had some issues with nouveau myself. When you get to the resolution selection prompt, choose vesa and set 1024x768. Reboot from there. This will let you get into gdm so that you are able to login xfce4. There you can uninstall nouveau driver using gslapt. You'll want to make sure you have installed kernel src, and you can get the nvidia driver while you're still in gui.
Before installing Nvidia driver, make sure to uninstall nouveau driver and reboot first.
also, you can try boot from tui then command as root
removepkg xf86-video-nouveau
Also, I was second guessing on the problem description. If it is that you are not able to even get to the installer stage, then at the CD's boot prompt type this:
install
press enter key and this will get you to use the text installation.