I have broken my S4 glass and figured i would repair it since the Glass is about $11 on Amazon. You do need the following
-Plastic Razors
-Regular Razor Blade
-Heat Gun or Blow Dryer
-Infared Thermometer ( Not needed but helps knowing exactly what temperature your glass is)
1. Remove the battery and sim card and sd card from the device
2. Using the heat gun or blow dryer Start heating up the glass to about 190 degrees (i usually keep it at 200 just to make it easier for the glass to seperate from the LOCA GLUE but be careful because direct heat in one are will burn the lcd)
3. Once at desired temperature, using regualar blade, place razor on the upper right corner underneath the glass and in a up-ward direction slowing slide the blade down, once you able to get the top half of an inch off the lcd, use the plastic blades and slowing slide down the right side of the glass and the loca will seperate ( apply more heat if you notice the glass isn't separating as well FYI Try to keep the glass at 180 degrees at all times if possible)
4. Do the Same thing on the other side of the phone untill the glass comes right up( Notice********** YOUR BOTTOM BUTTONS ARE CONNECTED BY ADHESIVE TO THE GLASS, BE CAREFUL WHEN REMOVING THE GLASS AND MAKE SURE YOU USE A PLASTIC BLADE REMOVE THE BACK BUTTON, HOME BUTTON, AND MENU BUTTON FROM THE GLASS BEFORE YOU TAKE THE GLASS OFF COMPLETELY.
5. Once glass is off remove the left over glue with your fingers, its comes right off. and to remove any finger prints and smuges make sure to use rubbing alcohol to clean lcd with a micro cloth.
Now are far as applying the new glass ive done it a few way:
-Create a border with 2mm adhesive around the lcd and around the rim of the device and reapply the glass
or
-Sams as above but also install a screen protector between the glass and lcd/digitizer and then apply the glass. that way it creates a barrier between both the glass and lcd.
or
Same as first way but order some Prokit UV glue LOCA Liquid 50g optical clear adhesive for samsung LCD repair on amazon and apply between the glass and lcd, once in place make sure to push all bubble out and to seal/cure the screen place in sunlight for 60 secs.
Hope that helps alittle. if anybody has any questions let me know