Turn the iPad off completely. Connect to the USB on the computer while holding down the home and power buttons. That will send it into restore mode. From there, iTunes will pop up on your computer. Click on restore and update. Confirm the update and restore. It will turn the iPad off and on as it extracts the software and resets the iPad. This should send it back to factory settings unless it is locked with an Apple ID. If so, enter your information on the computer when it prompts, and you should be all good! Update: Turn off the ipad. Plug in your cable. Turn on your iPad and hold down the home button at the same time. If that doesn't work ,then pull up iTunes on your desktop and then try the process all over again. The power has to be off, though, on the iPad.
Sounds like both, the backlight issue could be the result of not turning off the iPad before disconnecting the digitizer and LCD. That's called perm dim. It requires changing a chip and coil and intricate solder work. Did you try a hard reset? Holding down the menu and power button at the same time?