this is technically impossible unless you have vacuum chamber which would fit the screen. LCD is glued directly to the glass. even if you somehow safely separate it, you wont be able to glue it on new screen without air bubbles which could only be removed by vacuum. [br]
use UV glue to reduce visible cracks. FT-12 (search for ft-12 iphone glue on aliexpress) masks minor cracks and makes them almost invisible. keep it aways from skin/eyes.