I found when replacing hard drive the most difficult task is to replug the Display data cable back into the logic board. There is just so little room to work, I damaged the data cable plug contacts and the display would not work. For me work around was to order replacement data cable and install first on logic board before trying to mount and connect other display cables. And installing data cable to Display socket last. This end is larger and more robust up near the top edge of the Display giving one much more room to work.