I'm not a monitor expert, but I have connected WG monitors to a standard JAMMA cable. WG monitors use a special connector. Our JAMMA harnesses use a standard connector. Actually, there's really no standard, but this is as close to standard as I've seen.
I do not know of any JAMMA harnesses that have a WG connector, but there might be one.
All you need to do is find out where to connect your RGB, Sync and ground wires. When I've done this I've cut off the connector from an old computer power supply which fit my monitor connector. Hopefully your monitor came with a wiring diagram.
WARNING: Make sure you don't mess-up the connections or you could fry your board or monitor!!! Make sure that doesn't happen as I can't be responsible if it does. I might suggest you try to find someone locally who can come help you out. Maybe a BYOAC member in your area?
If you want to return your JAMMA harness I will give you a refund minus shipping costs, as long as it's in like new condition. Of course, if you cut off the connector we can not take a return.
-Mike