How do I test and repair the inverter system of my mbp?

Black screen of death, but I can see the screen when I shine a flashlight through it and it works with an external display. The keyboard backlight is still working, but not the screen. I haven’t had any spills or drops, but this has happened before. It magically fixed itself last time and lasted for another year. It seems I’ve run out of luck.

I’ve reset the SMP, PRAM, and all of that, and I had an Apple person look at it. They said it wasn’t the display cable, but they’d have to send it in. I’m thinking it might be the inverter system (screen, inverter, inverter cable, board) based on some googling I’ve done. What do I need to do to test this? Where is the inverter cable/board?