How to inspect the currently used Nvidia driver version and switch it to another alternative?

List available drivers via

% apt-cache search nvidia | grep -P '^nvidia-(driver-)?[0-9]+\s'
nvidia-304 - NVIDIA legacy binary driver - version 304.125
nvidia-310 - Transitional package for nvidia-310
nvidia-319 - Transitional package for nvidia-319
nvidia-346 - NVIDIA binary driver - version 346.59
nvidia-driver-390 - NVIDIA driver metapackage
nvidia-340 - NVIDIA binary driver - version 340.107
nvidia-driver-418 - Transitional package for nvidia-driver-430
nvidia-driver-430 - NVIDIA driver metapackage
nvidia-driver-435 - NVIDIA driver metapackage

and install with, eg

sudo apt-get install nvidia-driver-435

Show driver in use

• nvidia-smi

  Sat Sep  5 11:57:22 2015       
  +------------------------------------------------------+                       
  | NVIDIA-SMI 340.76     Driver Version: 340.76         |                       
  |-------------------------------+----------------------+----------------------+
  | GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
  | Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
  |===============================+======================+======================|
  |   0  GeForce 9800 GT...  Off  | 0000:01:00.0     N/A |                  N/A |
  | 65%   52C    P0    N/A /  N/A |    271MiB /  1023MiB |     N/A      Default |
  +-------------------------------+----------------------+----------------------+
  
  +-----------------------------------------------------------------------------+
  | Compute processes:                                               GPU Memory |
  |  GPU       PID  Process name                                     Usage      |
  |=============================================================================|
  |    0            Not Supported                                               |
  +-----------------------------------------------------------------------------+
  

• nvidia-settings

  

• nvidia-settings -q NvidiaDriverVersion

    Attribute 'NvidiaDriverVersion' (sturm:1.0): 340.76
    Attribute 'NvidiaDriverVersion' (sturm:1[gpu:0]): 340.76
  

• cat /proc/driver/nvidia/version

  NVRM version: NVIDIA UNIX x86_64 Kernel Module  340.76  Thu Jan 22 12:11:08 PST 2015
  GCC version:  gcc version 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
  

Just open the additional-drivers app, search for it in the dash, or in software and updates

In 12.04 you can download an additional drivers app HERE.