Here's an idea to verify if your hard ware needs to be replaced or not:

Download Ubuntu (an alternate operating system) and save it onto a USB device. Start up your computer from the USB device (you don't need to install anything; the computer will use the USB device as the main device to boot up from). After the Ubuntu operating system loads up, try playing some audio from within this operating system (the audio drivers should automatically be detected within that operating system). If the audio works perfectly in there, then it's some sort of driver issue within Windows that makes the audio not working. If there's no audio, then your hardware is likely to be broken and needs replacement.

But first, this just popped in my mind: See if you can download from the ASUS website the driver for audio for the computer model. After that, see if you can install the driver using this method:
Driver - Install in Device Manager in Windows 8