Reinstall X-windows system

I have a RHEL6 Workstation with a Nvidia CUDA-capable video card.  Recently, my X-windows system crashed and I have been unable to restart windows.  I have tried using older kernels and re-installing the Nvidia drivers, to no avail.

I am comptemplating re-installing the X-windows system.

Would it be safe to use:

yum group remove "X Windows System"

yum group install "X Windows System"

How should I keep track of packages that would not be reinstalled?  What services would I lose?

Do you have some advice?

I greatly appreciate your help.

don burgess