Possible to upgrade? Dell XPS L702X, looking for upgrade to support game

Dear Sifus, i bought this lappy about 2 years ago, it does decent job in some games but in some other games the fps might drop to 5 in certain areas(minecraft with tekkit, no problem with SC lowest setting). Below is the specs.

Manufacturer: Dell
Model: XPS L702X
Processor: Intel® Core™ i72630QM CPU@ 2.00GHz 2.00GHz
Installed memory(RAM): 6.00 GB
System type: 64-bit Operating System
GPU: Nvidia GeForce GT 555M

Can any sifus help me out with what i can upgrade to improve my fps? if possible can tell state the extimated price and location?

Thank you