Conics claims the LCD is "for ALL SL-C700 / C750 / C760 / C860and ALL SL-C1000 / C3000 / C3100 / C3200," so I'd guess they're exactly the same or so close that they're interchangeable.
Sorry, I put it a little unclearly. I've seen Fotos of SL-Cxxo's where at least one of the small symbols on the screen (the ones for "home, mail, etc." was different than the ones on my c1000. So I wondered aside from size and interchangeability, whether they are the same in terms of color quality, brightness, etc.
You seem to have both, a C3100 and a C750, so what do you think? Do you see any difference? (well, actually I'm sure you would have told me already if you did )
I could buy a broken c860 for about 80$, so I might give it a try... the only thing that worries me is my inexistent experience in repairing something like a zaurus... so I'm trying to find some how to's or pics...