Personal experience says that taking the laptop apart isn't actually all that difficult if you've got a small enough screwdriver(s), but it is intensely time consuming, especially if you're giving your first go at it. Me and a friend took apart mine to do some cleaning, ended up taking 6-7 hours from disassembly to reassembly -- incidentally, a second pair of hands is incredibly helpful. Also, if you've got warranty, that probably voids the crap out of it. Quick E: You'll also need a pretty sizable amount of flat space. It'd be pretty easy to fill up a good sized table with parts as you take stuff out of the thing. Quick E2: Check with your model's user manual to get a good idea of how much would have to come out of the lap top before you could get to your video card, by the way. Stuff probably both has to come out and go back in in a specific order.
Biggest issue is going to be finding a video card that's compatible, and blazes if I'd know how to help with that. Might give a shot at sending an email or phonecall in the direction of whoever manufactured your laptop, seeing what the computer supports. If it supports anything better, at least. Then it'd just be a matter of finding someone that sells whatever model card you need and ordering it.
And then taking the computer apart and putting it back together, of course. But no, as Jay says, there's absolutely no way to upgrade without disassembly.