VRAM for the dedicated graphics chip cannot be easily replaced if and when it goes bad. It is soldered into the motherboard. Unless you are extremely good at soldering replacing bad VRAM is something that should be left to the repair shop to do.
Generally speaking though, the more important question is which graphics chip are you talking about because all modern laptops with a dedicated graphic chip (or mobile graphics card in some very expensive gaming laptops) have 1GB of VRAM.
There are laptops with 2GB of VRAM, but that is mostly just a waste of money since you don't need that much VRAM until you hit 2560x1440 resolution. I really doubt even the most power laptop graphics card will perform well at that resolution.