what's the model of the laptop? I'm assuming since you have a 1st gen i5 and a 5470M its either a 7741G or 5741G. Most of those, BUT NOT ALL OF THOSE, had an available 5650M GPU w/ 1GB of VRAM option, so if you can find a MOTHERBOARD for your model with THAT upgraded chipset, it might work... but it would cost probably $200 (US) to do everything...
See my video, I upgraded my 7741 with Intel HD graphics to a motherboard with your 5470M:
http
/www.youtube.com/watch?v=QwwzqsiJMTE
Honestly, for as much effort and money, its really not worth it. While the 5650M is a decent mid range GPU chipset, its starting to get a little aged.
If you are willing to attempt the upgrade, make sure the seller has a picture of the ACTUAL motherboard...