No dice on the GPU. Graphics cards on mac laptops (and almost every laptop) are not upgradeable.
RAM as you said is very easy, take out the battery and there are three screws that you need to remove to get access to both RAM slots.
You can Upgrade the Hard drive, but it is not considered user removable and unless you are really comfortable tearing apart your laptop I'd say take it to an apple store or apple certified repair place to get the HD swapped out.