Adding this comment in its proper place:

After flipping up the metal retainer, pull it sideways.

Do not pull it up vertically.

Joe in PA

I added your comment in the proper place at Step 7

It would be easier to detach the Display Data Cable at its connector on the far right in the picture, since there doesnt seem to be much play to undo the suggested one.

A clearer explanation of the orientation is needed here. The bar code is at the top left of the iPad when you are looking at the screen.