i believe most of us have had the touch screen protector problem (good protection, but lousy visibility).
If visibility is your problem, you can use the ClassPad without the protector. As long as you only use the stylus that came with the ClassPad and you don't plan on taking it rock climbing it should be OK. I took mine off a long time ago and I've never had a problem.
We have a few dozen ClassPads where I work, and everyone has taken the screen protector off.

There is one ClassPad that does have a small scratch on the screen, but the guy who uses it is pretty rough on it. I think he carried in his jacket without the plastic cover and his car keys scratched it.

His ClassPad still works fine though.
NOTE: If visibility is your problem getting a replacement screen protector from Casio probably won't help. You'll probably get the exact same type of protector.