I'm afraid it's bad news. Laptop GPUs are soldered onto the motherboard (as is the CPU)...
This is subjective to the model.
Your model doesn't have much upgrade potential. Here are some considerations, though:
CPU: 820QM; 840QM; 920XM; 940XM - These are first generation models. You cannot upgrade
past this generation.
GPU: 470M; 480M; 485M - It's unlikely you will be able to upgrade beyond the 400M series. See below.
Keep in mind that your computer's BIOS may not support any of these upgrades. Further, what I don't know is whether your GPU is an MXM card or a chip soldered to the main board. If it's the former, then things hinge on the BIOS; if the latter, you cannot upgrade the GPU.