Hey, first I should say I'm just a fellow newb, but here's how I got the Nvidia drivers loaded.
First, make sure that the version of gcc used to compile your kernel is the same as the current one you have ready to use. gcc -v will give you the current one, and there's a command to find out your kernel version that will also show the gcc used to compile it.
Next do the following:
apt-get install module-assistant
module-assistant auto-install nvidia
apt-get -t testing install nvidia-glx nvidia-kernel-common
Then Edit your /etc/X11/XF86Config-4 file and comment out the Module entries Load glx and Load GLCore. Add the Module entry Load glx if its not already there. Also, change the device name from vga/vesa/nv whatever you have to nvidia and change the color depth to 24.
chmod 0666 /dev/nvidia*
chown root /dev/nvidia*
That worked for me and you don't even have to worry about compiling or downloading the thing manually.