it can be as easy as taking the television apart and soldering in a new power button.
it could be as ugly as needing a specific resistance of the power button to keep the circuit safe and healthy when you use the power button.
that is why some electronics repair people prefer to be 'in association' with the company of the product.
that way they have the information available to get the right resistance the first time.
some people are willing to try with a high ohm button.. and then again with a low ohm button.
but then again..
some people are smart enough to analyze the circuit to determine what the safe resistance is.
the knowledge here can really help a repair person's experience go the extra distance.