I just replaced LCD + Digitizer on my wife's. Her digitizer was shattered, and I was unable to separate it from the LCD because it was so shattered, in fact, i tried, but ended up ruining her LCD. The LCD+Digitizer itself is fairly straight forward to replace, the hardest part was getting the battery out.
you can follow the videos on youtube for tear-down of a 1520. Getting to the battery isn't even that hard, but getting the battery out is a little difficult, but just be patient. You may need some new double sided tape to hold the new battery in place. I would say this is a medium-low difficult installation.