Just posting a general comment in case it helps anyone . (If this is inappropriate the nods can remove it.) My son had a...

The old adhesive CAN work but if the screen is cracked and there are bits of glass in it like mine then it is difficult to reuse the adhesive. The difficult part is finding adhesive and applying it since the edges are so small. I just went without any additional adhesive and it still sticks pretty well though I can tell it's not stick 100%. If anyone know what adhesive to use and how to apply it in very small quantities that would help. It seems like the factory adhesive used it like a black sticky tape. And putting down a width of 1 to 2 mm of it on the thin edge will be VERY difficult.

From the instructions it says that the glass can not be separated from the LCD.