Im a bit exasperated from going over alot of data so what follows will probably sound retarded. This is what Ive figured out from staring at these forums / wikipedia and google all day. PLEASE correct me where Im wrong, or add pertinent info!!
Ok, GNOME is just how the desktop looks, its a 'skin' that can be switched. Unity is the default skin for 12.04. GNOME and Unity dont care what driver you use for your video card. If youre having problems with an ancient nvidia driver, digging into GNOME or Unity isnt going to help. I have no idea how to switch between GNOME and Unity (although I did install GNOME)
Nouveau is a catch-all for graphics drivers : if you dont have a video driver installed, this will run the video. I have no idea how to check if nouveau is 'running' or how to 'run' it. I have no idea how to switch to / from it.
Jockey is a built in program that makes it easy *cough* to switch drivers. It does not work with all drivers.
Nvidia does not currently have drivers for the geforce fx 5300. If you have 2 monitors, the best you can get is the same image on both monitors with the settings->Displays telling you that you are using a pink screened laptop.