LCD does not turn on after I disassembled the MacBook

I have a problem with the LCD MBP 13 mid 2012 I after I changed the keyboard, LCD suddenly died I was very sorry to have unpacked it, then I tried to use the Converter to External Monitor to make sure the machine was running, and luckily the monitor could display images, and mean Logic  Board is safe, does my LCD macbook really need to be replaced?  Can my LCd still be used for life?  , then I also experienced a problem when my Charger Cable Macbook turned on by itself without pressing the power On, is that normal?  and if it's not normal how do you fix it?  thank you in advance, I hope this problem can be resolved thanks to the help of friends at Ifixit