I'm almost finished doing the install you're after, and by chance I'm guessing it's in the same car. I have a VXR8 LS3.
When you say the screen has VGA, is this something you've got info about. I couldn't get the pinout for the headunit, so have used the Rear Aux input which is composit and so not as clear as it could be if there are vga pins.
My car has the factory fit SatNav (Rubbish), which I've yet to remove, so the PC is in the boot. You don't really need to touch the PC unless you want to play DVD's, so it's not neccessary to put it in the glovebox (A bit tight I'd say).
Let me know what info you need, I'll help if I can