Congratulations on a great find! And heck, now you've got $300 to spend on parts!
If you can't repair the existing monitor, you can get a monitor with the same size specs from Wells Gardner so it will fit in your cab.
The easiest way to run Windows with a standard resolution arcade monitor is to use the ArcadeVGA from Ultimarc (
http://ultimarc.com/avgainf.html). It will run Windows 640x480 interlaced, and pretty much all of the Mame games will run at their original resolutions.
Wells Gardner also sells some large VGA monitors for a little bit more money. I have never seen one in action, so I don't have much to say about it, except that people around here seem to really like it. On of them is the D9200, I believe, and I THINK it lets you run 640x480, 800x600 without interlacing, and also will run at standard arcade monitor resolutions, so you might have the best of both worlds... Again, don't take my word on that!