Just unplug everything and place your computer case on a flat surface, then take out the case side panel. Get some compressed air cans and blow the hell out of it. Remember to keep the can straight or it might drip. I also use a rag to clean flat surfaces.
My case (Antec 902 v3) has dust filters in a few places, so I also take those out and wipe them, then blow the edges. They are actually washable but I'm too lazy for that.
In the case of your GPU, blow air into the slots trying to get the dust OUT. Also blow the fans since those catch a lot of dust in the blades. For the CPU heatsink simply blow in the direction of the holes, assuming you, like most gamers, have a relatively tall aftermarket heatsink.
It's all really straightforward. You don't really have to take out the internal components.
My case (Antec 902 v3) has dust filters in a few places, so I also take those out and wipe them, then blow the edges. They are actually washable but I'm too lazy for that.
In the case of your GPU, blow air into the slots trying to get the dust OUT. Also blow the fans since those catch a lot of dust in the blades. For the CPU heatsink simply blow in the direction of the holes, assuming you, like most gamers, have a relatively tall aftermarket heatsink.
It's all really straightforward. You don't really have to take out the internal components.