*Updated*: This is the link to the official instructions (too late).
The replacement power supply unit arrived from Infrant. There are no instructions accompanying the unit. So I started to look around the NV+ to see how I can open it up and perform the replacement:
1. Take out the disks after labeling them. I think their order in the NV+ is important. Make sure bay one goes back to bay one, etc.
2. Loosen some screws in the back and the bottom. Turned out I have to start with the sides, then the fan, then the bottom, which is the PSU itself.
3. Notice all the dust gathered inside. Look at the pictures.
4. Then it's a matter of taking the PSU cable off and plugging in the new one.
5. Don't forget to transfer the serial number sticker from the old PSU to the new one before sending it back!
6. Check out the burnt coil in the picture.
7. Finally, don't forget to download and install the plug-in to up the fan speed to reduce the temperature. Otherwise it will burn out again!
It's basically not too difficult.