If you are replacing a digitizer on a Lumia 920, make sure you use black adhesive. I just replaced one and if you don't use black adhesive, light leaks from the Windows home button and from the side. I made the mistake of using clear. It really wasn't difficult at all. The digitizer came off fairly easily using a hair dryer, suction cup, and a guitar pick. The replacement digitizer seemed to be of good quality and seated into the frame really well. The hardest part was removing the old adhesive and cutting the new adhesive to fit. I've replaced digitizers on iPads and iPhone 3gs but this replacement was the easiest by far. If you have a cracked screen, don't be afraid to replace it yourself. Just follow the directions in these 2 videos and you shouldn't have a problem:
Nokia Lumia 920 Disassembly & Assembly - Screen & Case Replacement - YouTube
Nokia Lumia 920 Digitizer Glass & LCD (TFT) Display Replacement - YouTube
Nokia Lumia 920 Disassembly & Assembly - Screen & Case Replacement - YouTube
Nokia Lumia 920 Digitizer Glass & LCD (TFT) Display Replacement - YouTube