I've got a friend who recently inherited an old arcade cabinet for this game, and the wiring on the controls is completely effed.
 
Does anybody know where I could find any kind of schematics or manual for this?
 
EDIT: I found one here a while ago, but the monitor turned out to be a dud, so it didn't matter. Nevermind, duders.

Well you can definately replace monitors in arcade machines. Sure it can be a bit of an investment, but I think to restore an MvC2 machine, it would be worth it. 
 
As for specific manuals or schematics I have no idea, but check this out  http://www.happcontrols.com/   
Those dudes are great for replacement parts, you should be able to find the right ones. I've been attempting to build my own MAME arcade machine for a while, but I kinda abandoned it due to a lack of tools. But I did a lot of research and bought books and other crap, so I at least remember stuff like this haha.