Is it difficult to change the power supply on a

No, it is actually very simple. Pretty much all you really need to do is have allready bought a power supply replacement and take the back cover off of your tv. Once you have the back off you will be able to see the power supply. Most power supply's I have ever messed with were only held down by four screws and have a few plug ins into it that you have to remove. Nothing hard. Just make sure that when your doing this that your tv is not plugged in or you may be in for a rude awakening.