The thing that trips me is the "aside from the power supply". If it's just the power supply, then most people would drop in a new power supply to get the price up. Right now, to my mind, that cab is "not working".
If you want to MAME it, then a bad PS is NoBigDeal as you don't need the power supply or the board. You do, however, want to be sure that the monitor is working. As paige points out, the monitor will be wired (it uses AC, so the power supply being dead doesn't interfere with the monitor). Unless you can establish that the monitor is working, treat it as if it is not.
Hopefully you can get some indication that it might be (e.g. that high-pitched whine, see the guns heat up, get an indication of raster on the screen).