I am trying to pull this from memory. I too was frustrated just as you are.
Do this first:
1) Determine if the main board is receiving power and its power-on-self-test (POST) is functioning. Position the TV so that you can look inside the back of it and can observe the main board, which is centered in the set. If the back cover is still in place, do not remove it.
2) Unplug the TV, wait until the amber light on the front of the TV turns off, then plug in the TV, don't touch the power button, and see if the two green LEDs glow when you apply power. One LED is located near the top of the main board and one is at the bottom center of the same board. I am not sure if you can see both LEDs with the back cover and internal mounting plate in place. I know you for sure that you can see at least one of them.
3) Within approximately 10 seconds after applying power, the upper LED will turn off and the lower LED will remain lit. If this does not occur, there may be a hardware/circuitry issue occurring that must be corrected first. I say this based only on the experience gained from working on my TV and some things gained from reading through the forums.
4) If the top LED turned off and the lower LED remained lit and if the amber light on the front of the TV is on, press the power button on the TV for one second and release it. The top LED should turn ON. If it is now on, proceed to the next steps.
5) Unplug the TV again, wait 10 seconds after the amber light on the front of the set turns off, plug in your thumb drive (Note on thumb drive: I made sure my drive was freshly formatted to FAT32, that the file was unpacked with 7-Zip and the contents are in the root directory, and that there are no other files on the drive. I can check my thumb drive later if you want to know a list of the files that should be present), and then plug in the TV. After the thumb drive flashes several times, wait about a minute and then press and hold the power button on the TV for 5 seconds and release it. The drive will flash again and I think it turned off again.
6) Observe the light on the front of the TV for five minutes. If it remains amber the whole time, press the power button on the TV again and hold it until the thumb drive lights up and immediately release the button.
7) Leave the television alone for 8 to 10 hours.
8) Remove the power cord from the TV.
9) Unplug the thumb drive from the TV.
10) Plug in the TV again and wait one minute. If the set does not turn on and show the (W) logo, press and hold the power button on the TV for five seconds and release it. Don't hold it in for more than 5 seconds.
11) If the process was the same as mine, the set will turn on, the light in front will be blue, and it will display the (W) logo for about 5 to 10 seconds. After that it may turn off if there is nothing connected to the TV inputs. If you want to mirror my experience, don't have anything connected to the TV inputs until after it powers on.
12) If the light in front remains blue, turn off the TV using the power button on the TV and connect a device to the inputs that you are sure is providing a signal. I connected my cable box to the component #1 input on the TV because that is what I always use. If the light in front was amber, do the same thing.
13) After connecting my device and powering up the set again, my TV detected the signal and displayed it on the screen. At this point none of the functions on my remote control worked except the power button. I powered off the TV, unplugged it until the amber light on the front turned off, plugged it back in, and pressed the power button on the remote. The (W) logo appeared on the screen and then switched immediately to the show playing on my cable box.
Let me know how you make out.