Cost To Fix This?

If you turn it on in a VERY DARK room with a very bright flash light, look to see if the panel lights up for a second or two, continually or stays completely black.

If the lights work for a couple seconds or stay black then the inverter is probably the problem (part number AH302195, reference number es7816, description IVA1904A HV PCB) but it's NLA as a separate part. you will need to replace the entire panel:

You can see that there is a picture there if you point the flashlight into the LCD display and watch for the video around the slight glow. This shows the T-con and the LCD display is working.

If the light stays on then the T-Con board or the LCD display is the problem and you will need to replace the entire panel.

expect the labor charge of around $150 plus parts