I do not have step by step instructions for this model, but here is a a general guide.
The TV needs to be unplugged and after it is unplugged, press and hold the power button for a few moments.
You are going to want to lay the TV down. It needs to be on something firm like a wooden table. You will need to lie something down before the TV like a sheet or table cloth to protect the TV from getting scratched, nothing thick. The stand may or may not need to be removed; I do not have a clear picture of how the stand is attached. Then the back cover will need to be removed. There should be screws all along the edge and a few in the middle as well as a couple around the inputs. After the back is off you should be able to see the power supply in the center top area. Most boards are held on by 4-8 screws. They need to be removed and any cables unhooked from the power supply as well.