Why is my laptop overheating after only a few minutes of use?

Overuse may be contributing to your fan overheating too quickly. Aside from simply lessening use, it might by better to shut it down completely, rather than just putting it into sleep or hibernate mode. As for getting to the fan and attempting to replace it, you would be aiming to remove the bottom cover of the computer base. The fans are generally placed on the back of the computer behind the keyboard and under where the top screen is. If your fan is heating up the base of the computer too much, your motherboard or other crucial parts and functions can be damaged, as well as damaging whatever surface your computer is being used on (especially your skin). After that, it's just a matter of getting the right part for your computer, and that can be found in parts shops and online in places such as eBay or the Asus official website.