A discrete graphic card can be upgraded by completely opening the laptop (Screen & all).
But this is pointless. Getting Mobile version of graphic card is difficult enough in US/UK let alone India.
The performance improvement will not be as good as a new laptop you can buy from the cards money and sale of current laptop.
EDIT : I googled a bit and 9300M is available for $200 in US.
^^ though it's decent gfx card it's overpriced - last time I checked Sapphire HD5570 1GB DDR3 was 4.6k and Sapphire HD5570 1GB GDDR5 was 5.8k
Guys nvidia is coming up with its dual gpu solution in the form of gtx 595. It will have 2 gtx 580 bridged together in a single pcb. Will be launched at the same time as Antilles from amd and both these cards will take on each other like never before.