How do you replace a cracked screen?

You have to remove the battery and heat the screen up to a uniform temperature of 160-180 degrees F. with a heat gun. Using a dental spatula or iopener gently start to lift the glass off of the frame. Never press down always using upward pressure. Be very careful not to scratch the plastic digitizer.Use extremely light pressure when lifting. As the separation starts you will see the loca turn loose from the digitizer. Pay extra attention to the areas around the button so not to tear the flex cables. Clean the old tape off completely and replace with new. Clean glass well and wipe off any dust. Make sure when applying the adhesive tape that the surface is perfectly clean or you will crack the new glass