me too. All went well expect replace this flat cable which is tricky almost when my view is low and I've got big finger. I broke the cable end connector to motherboard but I don't know if I damaged the connector on motherboard. I'm waiting from Apple service for diagnostic.

I would suggest on the guide to add a step to explain how sensitive is to replace this cable. iMac should lay on the back and it should have some stuff to maintain the motherboard elevated in order to insert the display port flat cable to the motherboard on a less stressful way.