Follow the steps below.
Especially for rear-access VACs, you need TWO people for this operation - one behind the VAC and one in front, holding the monitor, so that it doesn't fall out once the fasteners are removed.
Step 1:
Power off the VAC completely
Step 2:
Remove the screws holding the VAC control board, and pull board away from the VAC cabinet:
This will give you access to all fasteners holding the touch screen monitor in place.
In most cases, you do not need to remove the cables from the VAC control board, to gain access to the monitors mounting screws:
Note: The above picture demonstrates a control board being unmounted while it is still powered ON.
This is NOT recommended!
Always power OFF the VAC when it's main control board is being unmounted from the VAC cabinet.
Step 3:
Replace the monitor, re-connect all fasteners, and re-mount the VAC control board.
Step 4 (optional - for 1st Generation VAC Control Boards only):
If you were provided with a new Monitor Controller, then replace existing one.
A Monitor Controller looks like this;
Step 5:
Reconnect the three Touch Screen Monitor cables:
HDMI
USB (see note below)
12Vdc power
You can use your other VAC to cross-check the connectivity if you have 2 touch screen VACs.
You can also consult this article to see where all VAC control board cables are connected: VAC Control Board Connectivity
NOTE on USB cable
Older (Version 1) monitors use a VGA-style USB connector shown below.
While existing production monitors (one you received as a replacement) uses a standard USB Type B.
A standard USB Type B looks like this:
You should've been provided with the USB Type B cable, which you will need to use between the monitor controller (if one exists in your VAC) and the monitor.
On newer generation VAC control boards, the USB cable will connect directly to the VAC Control board instead of using a Monitor Controller
Below is a picture showing the difference between 2nd Generation and 1st Generation VAC control boards: