The easiest, most plug and play option is to purchase a JPAC (not an IPAC) and an ArcadeVGA3000 from Ultimarc.
The JPAC plugs directly into the JAMMA harness in your cabinet to connect the controls to your PC (including the coin slots). The ArcadeVGA puts out a 15KHz signal for your arcade monitor.
If the original game had extra buttons wired directly to the game board (i.e. Not part of the JAMMA harness) you'll wire those to the extra screw terminals on the JPAC. Don't worry, it sounds more complicated than it actually is.
I have a "big picture" diagram somewhere that shows how it all hooks together. I'll post it later when I have access to my PC.
The only part that doesn't have a plug and play solution is the sound. Usually people rig up something using a set of PC speakers. I have pictures of what I did with that too that I can post later.