This Guide worked and was expertly written!!! Thanks for the help my macbook screen now works again!!!!
When reconnecting the Hard Drive Cable to the logic board (Step 17) I ran the HD cable on top of the microphone wire, and the other wire that runs parallel to it, when I should have run the HD cable underneath those two wires. This resulted in the hard drive not being connected on startup, and a lengthy troubleshooting session to figure this out. So save some time and install this underneath the two wires, just like you found it when taking it apart!