If you go down to the application menu you can find a hardware configuration tool were you can specify a higher resolution for your monitor.
Or you can go and edit the /etc/X11/xorg.conf youself manually and tell it your horizontal and vertical refresh rates and maybe get it more accurate that way. Look on the internet for samples... Used to be /etc/X11/XF86Config, but they are pretty much the same.
Otherwise head on down to the nvidia website and install their propriatory drivers in order to get 3d acceleration. Read the "readme" file very carefully and it will tell you what to do.
Since your new to Linux it will be a pain in the rear, but once you get used to how everything works it's fairly easy and simple thing to do.