yeah, .tgz and .tar.gz files are the same. There's one distro (Slackware) with a package system based on those .tgz (you can install them with swaret, slapt-get, pkgtool or the tar method. Perhaps the difference it's that the .tgz it's usually used for binary packages)
rpms can be installed with urpmi or 'rpm -i --nodeps package.rpm'
about the nvidia drivers, just do from a system.console (Ctrl+Alt+FX where X it's a number, to change from graphical to framebuffer console):
Then edit your /etc/X11/XFree86Config (or XFree86Config-4 or xorg.conf ), depending of your distro. Put
in your graphics driver section and
if you don't want to see the nvidia logo
Option "Logo" "false"
I also needed to enable the irq for vga in the mobo bios