How can I replace default graphic driver with NVIDIA driver?

Question

My machine has 4 GPUs,

$ lspci | grep VGA
02:00.0 VGA compatible controller: NVIDIA Corporation GM200 [GeForce GTX TITAN X] (rev a1)
03:00.0 VGA compatible controller: NVIDIA Corporation GM200 [GeForce GTX TITAN X] (rev a1)
83:00.0 VGA compatible controller: NVIDIA Corporation GM200 [GeForce GTX TITAN X] (rev a1)
84:00.0 VGA compatible controller: NVIDIA Corporation GM200 [GeForce GTX TITAN X] (rev a1)

How can I use NVIDIA's driver for display the user-interface without any error, I heard that replacing the default ubuntu display driver with NVIDIA's driver will cause black-screen error.

Here are informations on driver and OS

OS: ubuntu server 14.04

$ uname -a
Linux ubuntu 3.13.0-88-generic #135-Ubuntu SMP Wed Jun 8 21:10:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:    14.04
Codename:   trusty

Driver:

$ cat /proc/driver/nvidia/version
NVRM version: NVIDIA UNIX x86_64 Kernel Module  375.26  Thu Dec  8 18:36:43 PST 2016
GCC version:  gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3)

Xorg:

$ cat xorg.conf.failsafe
Section "Device"
    Identifier  "Configured Video Device"
    Driver      "vesa"
EndSection

Section "Monitor"
    Identifier  "Configured Monitor"
EndSection

Section "Screen"
    Identifier  "Default Screen"
    Monitor     "Configured Monitor"
    Device      

"Configured Video Device"
EndSection