You can check the version if you install Synaptic:
You can use Synaptic for changing the driver. First try nvidia-current, then nvidia-173, then nvidia-current-updates and maybe finally even nvidia-experimental-304 and nvidia-experimental-310.
sudo apt-get install synaptic
Stay with the driver that performs best, and only try the experimentals if there is really no good alternative.
If you lose display because of a driver change, you can repair it as follows:
(item 1, left column)