This is a difficult guide so make sure you are completely prepared before doing it. It should take 30 minutes to an hour. Begin by putting on your anti-static wrist wrap so you do not damage any other components. Make sure you do not use too much force especially for the clips located at the keyboard. Along with this the ribbon cables are no force needed to insert them (ZIF) so do not apply force while removing them. Also do not remove your keyboard or motherboard without disconnecting the cable underneath because it will cause damage.
The heat sink and thermal paste can be found making direct contact with the CPU. Over time thermal paste can become less effective at transferring heat to the heat sink, Which is why it may need to be replaced.