You didn't mention your distro, so answers are general.
Install the kernel source and kernel headers.
Did you install the developmental packages if you choose to use source code?
Edit your /etc/inittab and use the number in the comments for the default that corresponds to "Full multiuser mode". You will boot into command line then and you can start your X session with startx.
# Configuring X
Linux Hardware Compatibility HOWTO - video cards
The Linux XFree86 HOWTO
Common X configuring tools:
Redhat 7.3 down - the setup
utility leads to several config tools
Redhat 7.3 up - redhat-config-xfree86
Debian - dpkg-reconfigure xserver-xfree86
You may have these tools:
nVidia Driver Installation NHF
nVidia driver page