Johnny Nero? From 2004? It wouldn't suprise me if a game that recent used a VGA monitor. From the pictures it looks like a 25", those can be hard to come by depending where you are. Also you may be able to make a few bucks off the guns, since they wouldn't work with an LCD anyway. All of this said, you may be able to use monitor already in the cabinet.
As far as control panels, you would probably have to cut a new one, but I honestly haven't seen the cabinet or the control panel so you may be able to cut a section from the cabinet to act as a "shelf" for the slickstick.
Removing the monitor is easy. Just don't touch the electronics or stick your penis under the suction cup on the tube. There are several capacitors on the chassis board and the tube itself that need to be discharged, it's probably best done in the cabinet. There are plenty of videos of how to do it on youtube. It's kind of scary the first time you discharge a high-voltage cap, but if you take the right precautions (i.e. not using your tongue to do it), you should be ok. It only takes a screwdriver and some thick wire