While not quite 10 years old I don't see a lot of posts in TV repair forums.
http://www.cnet.com/news/get-an-insignia-55-inch-roku-tv-for-449-99/ gives us a clue that repair may be more than replacement.
But give it the old try of unplugging it from the wall and remove all cables then wait a hour to let it reset what it can. Apply the mains only and see if it powers up.
My 8 year old Sony LCD TV KDL-52XBR3 has suddenly quit on me. When I switched on the power, the green button light fades away within several seconds with no picture and sound. Any idea what's wrong? Thank you all for your assistance.