Can you fix an externally cracked plasma or lcd screen?Probably not. It's a vacuum chamber and when it cracked, it let air into the envelope.
The again, if it's still working, your TV may have a plastic cover over the screen to protect it.

One thing I do know first hand, is that the cost of the screen replacement will probably be more than the cost of the TV itself. try to get a second hand tv from ebay that it doesn't turn on but the screen it can be in a good condition replace the broken screen your self or I'd suggest you use your home owner's insurance and replace it.