Well, I know you can upgrade the video cards in the Dell 8000+ models. I do not see your laptop listed in your rigs, but if it is a Dell, there are hundreds of accessories you can find for them on eBay for a very decent price...when compared to Dell's prices anyways. They don't look to difficult to install, but you never know for sure. If you're considering upgrading the video RAM only, I highly doubt you can do that as you can't do it with desktop models...well..except for an old ATi 8MB I have come across.
Good luck and I hope this helps!