I have repaired several hairline cracks, but not that long. The process should be the same, except I am guessing that took a little harder hit and I would check behind the center of the cracks, where it looks like it took the initial impact and make sure there is no splintering at all. More than likely you are okay. Here is the Dremel bit that I use to remove the cracked gel. You have to have a pretty steady hand or it can get away from you and take away more material than you planned.