Anyway...no matter what Nvidia driver you're trying to build for your kernel, you will need to install the header package for your kernel, plus the compilers to build the free part of the driver source.
A more complicated way to do that is in the Debian wiki entry on Nvidia drivers, which everyone should read first before trying and install, but an easy shortcut is to install module-assistant, then as sudo or root:
and answer yes to any questions. This runs some scripts to get compilers and headers for you from the standard repos. (Debian backports repo kernels probably require more hands-on approaches)
