Its kind of hard to find a upgradeable video card for a laptop as usually the video hardware is integrated. Different video cards many also not fit as laptop cases are all different. Upgrading laptops is not as easy as a desktop, but you could upgrade the ram, hdd, cd drive easily.
WoW doesn't require that much gaming power either. My 1.5Ghz single core 1024memory laptop can play it fine. Probably any dual core with 2gb of ram would be able to play it on high.