You're going to need to keep mains power for the monitor. Keep it on that iso transformer,though, or you're not going to have a monitor for long.
In fact, pretty much the only thing you should need to change, assuming this cabinet is in the JAMMA standard is unwiring the power supply. The J-PAC takes care of your controls when you plug it into the JAMMA socket, as well as amplifying the video signal from your video card.
Heck, depending on what OS you want to run, you may not even need an ArcadeVGA.