Well unless u get one of those desktop replacement uber alienware laptops that takes cards and 3.5" hdds, otherwise known as customizable, really expensive, giant laptops.
Otherwise...cpu (only the same generation)
GPU - never tried soldering a new chip onto the m/board directly...so for me its a NO
cpu is a piece of cake, open it up and drop it in. make 1000% sure it's compatible first by checking forums though. Things like FSB can make all the difference. Laptops can be persnickety.