I attempted this with Lumia 920 myself and ended up breaking my old screen completely. I did my 920 cover replacement myself so I was fairly comfortable with taking it apart. The screen has many parts(there is a plate behind the glass and other important stuff), so make sure you don't break the parts you need like I did. Turned out to be really hard for me because i had to take apart the glass from the metal plate behind the glass. You would really need a suction cup if you're planning to take off just the glass from the front, I can't stress this enough because you might end up breaking other parts of the phone if you don't use suction. Also, heat up the adhesive, not just a little bit but sometimes you really need to put it in front of a blow dryer for a good one minute or so. Not trying to discourage anyone but its kind of a hassle so I'd just get it repaired from a professional.