I agree with alexh!! This is the real fun part!!! :-) You don't want pre-built..
As for AdvanceMAME, it's basically a user perference.
If you will only be running Arcade games and are OK with some DOS (setup/configs) commands, AdvanceMAME is great.
If you are really wanting Windows and/or want to run programs other than MAME (other emulators, games, etc.. <shudder.. ;-)>), then the soft 15Khz option is better.
And about the "damaging the monitor", I use a jpac as Eny- does. It's great. But it's designed for a JAMMA cab, and I don't think your cab is JAMMA. (??) And you already have a wiring harness...
The ultimarc site might (probably) has an option like the jpac just for the video. If so, that's nice and safe. But again, I'm not sure that it supports 25Khz. So you still might not be able to use it.
Our cabs (I think??) are 15Khz...
The other option is just to make sure you turn on the PC first and then, when the OS (AdvanceMAME or Windows) is up, THEN you turn on the monitor...
Someone somewhere (helpful, huh?) actually made a circuit that I think ran off of a PC printer port that would turn on a monitor AFTER the app had run just for this, but I think that's overkill for you.. ;-)
It really is fun, and once you play your first game on your cab, it feels awesome!!
The more complicated the install, the better it feels!! :-)