I was under the impression that i didn't need light bars since it was a CRT. But i don't know much about any of this.
okay, i see what's going on here... you asked a few different questions initially kind of all mashed together and now the answers you are getting have you mixed up. let me explain a little bit about how light guns work and hopefully this will clear some things up.
the Wells Gardner D9400 is a CRT monitor. it will work just fine with light gun games using a regular optical light guns. these guns work by flashing the game screen with white when you pull the trigger... and timing how long it takes for the gun's optical sensor to "see" the white be drawn on the screen. this is usually done a few times in succession to ensure the machine is right about where it thinks it is. this process takes about 1/4 to 1/3rd of a second.
this works because the CRT "draws" the image left to right, top to bottom, line by line. we know how long it takes to draw a whole screen this way and by timing how long it takes for the white light from the CRT to reach the position where the gun is, we can guess pretty accurately where it's gonna be.
this type of gun does not work with LCD monitors because LCD monitors wait for a whole frame from the device it's connected to, to be received, and then updates the whole panel all at once. there is no "drawing" the screen, so there is nothing to time against. just a (nearly) instantaneous frame change from one to the next.
if you had an LCD monitor, and wanted "lightgun games" you have to use the camera style guns that track infrared LED's placed around the monitor so the computer can figure out where it's being pointed.
adding an LCD marquee to a cabinet with a CRT will not affect how the optical guns work with the CRT.
in a nutshell if you plan to keep the WG D9400, you needn't concern yourself with changing it to add the LCD marquee or lightgun games.
if you plan on changing the WG D9400 for some other LCD monitor, you will have to go a different direction with regards to light gun games.