You have to install the rpm for rpmbuild. Its a seperate package not installed by default it seems.
I am kind of frustrated myself with NVIDIA's linux support. Seems like some people have had success but not bothered to come back and report how. I'm still trying to install the drivers in RH8 and getting network problems with the driver.
Reminds me of the old tulip vs. Linksys days...
...And now abideth faith, hope, charity, these three; but the greatest of these is charity.