Doug Stewart writes:
Errrm, that second one should be "GeForce FX 5700".
And the install is dead easy: download the nVidia installer and run it as root, then edit /etc/X11/XF86config to reflect "nvidia" instead of "nv". If you want instructions on dualhead mode, search nVidia's docs for "TwinView".
Any nVidia should be just as easy since they now use a unified driver. As another data point, I'm using a GeForce FX 5600 for my dual head setup.