Yes, but that's what he did do and he had problems. If you only install packages that RH supports you will not have a problem. But as soon as you do install pakages that they do not support, or make mods etc, you will have a problem. I also say stick to up2date, however keep around the packages that are not RH supported because you will have to reinstall them if an update ever crushes that package.
In this case I'm imaging that he installed the NVIDIA drivers packages eraly on. When he updated his kernel, he removed the links to the objects which the NVIDIA packages created. So know he needs to re-create those links in the kernel by reinstalling the NVIDIA packages for the appropriate kernel version.
I would simply do a rmp -e for NVDIA_kernel and NVDIA_GLX
There were bugs with the update of GLX. So you must uninstall and not update.
Then reinstall the new .18 packages.