Broken Screen iPhone 4

My iPhone 4 cracked the screen (second time). At first I bought a screen that included the glass and lcd with touch digitizer that was about $19 and it worked perfectly. But looking back I saw that some vendors sell only the glass, which is much cheaper. The question is: If I buy only the glass I'll be able to change it normally or need to buy a complete piece (glass + lcd +digitizer)?



[1] Glass+lcd+digitizer: http://bit.ly/18d5Wfd
[2] Only glass: http://bit.ly/19IRskA