It is possible to damage hardware with incorrect settings... however the X server should never allow you to do that (SHOULD) so if it is working somewhat now you're basically safe unless you start using modified code or other programs to adjust the hardware. Use XFree86 supplied code, plus nVidia drivers, and you should not be able to damage the hardware.
I have no idea what you are referring to with 'turbovision', you'll need to explain more about what this is before I can help you with that.
"..the triumph of evil is for good men to do nothing."
VIDIA video driver RPMs for Fedora
:: see yum repo at livna.org