This is by far the hardest part of the entire replacement. I ruined my screen doing this, you might as well buy a new screen at the same time as you buy your battery. I just barely rubbed the edges of my screen and it turned the edge of my screen purple. This eventually migrated to the entire screen causing the whole thing to be purple/black.
I have this same problem, but I have little flickers on the screen, but no picture or anything.