They are all the same as far as this goes. (More or less.)
Download nVidia's proprietary Linux drivers here:
As root, chmod 755 and then execute the file you download.
This will build and install the nVidia drivers.
You will need to restart X11.
You can skip manually creating an xorg.conf file. (If you want to, though, this is the file to edit for the whole dual screen thing.)
Instead, open the nVidia configuration utility. It will show up in your K menu / Gnome menu, or whatever you use. Or, alternately, you could execute "nvidia-settings" from an xterm.
You can define and set relative positions, color depths, and resolutions for your monitors from this window. Remember to click the "Save to X Configuration File" button if you want your settings to stick around next time you start X11.
If you want some enlightenment from this, read your /etc/X11/xorg.conf file once you are done.