After fixing my home button with ifixits replacement I accidentally bent the LCD cable when I put it together and caused the screen to fault.
This was simple for me to repair as I have alot of experience with iPhone repair but most people should be able to do it if they have the correct tools and workplace.
Keep track of your screws and their locations.
Be very careful with your logic board when you open any iPhone 4 as the small blue inductor fell out and I had to fix with solder which is not as simple as the screen
Try not to squish the LCD cable when reassembling.