You need a package for the rpmbuild command
You need the rpm-build package.
:-) Install it off the CD, or wherever you got all the other RedHat 8.0 packages.
Compared to Windows, the driver installs on Linux are very raw. Linux is pretty much designed to have all the drivers ship with the kernel, and nVidia, because they have closed-source drivers (even for their motherboard, which is even more stupid and ridiculous than for their video card) break that system, and so are a big pain.