Sorry this is going to be a bit long, but I have an iphone 3g with a cracked glass like i've seen a lot of people have, and I haven't been able to find too much detailed info that helps you change just this part. First off i'd like to say this was on the difficult side to get apart so good luck if you attempt this! I used ifixit.com which was the site that came the closest to revealing this information and the youtube video from pdaparts for the information on how to take it apart. This is meant to help someone who has a pretty good idea on what they are doing and has hopefully watched some videos or read some tutorials. So here is goes:
1: The first minor issue I came into was when I went to pop the screen off to open it up. By the way I took this apart with the tiny screwdrivers you get at the real dollar stores and box cutter knife
That said I highly recommend getting one of those blue pry tools as they make life a lot easier. When taking the screen out I had to "rewind" the video a few times to try to catch where they were prying this apart. so here is a picture to help better illustrate how to get this thing apart after removing the two screws:
2: I don't have pictures of this but as a side note when I tried to pop the lcd away from the digitizer it was flexing quite a bit and wouldn't let go! What I did was run the knife between the two metal brackets you just unscrewed and popped one side off at a time; it came off pretty quick and easy when I did it this way.
3: This was where most videos and info went cold...I guess the screen just magically fits on at this point lol. What I did here was follow the info from ifixit and heated the sides first to free the sides of the plastic frame from the glass screen and digitizer. This gave me a point at which I could continue to work the screen away from the housing and it came off pretty easy. Next I spent quite a bit of time slowly heating and prying the speaker area away fromt the plastic housing. This is held on with double sided tape and after heating I carefully used a knife to help free it. Next I pryed the home button area free using the same method...if you happened to need to replace the home button you are all set to do so now. (Wow hope I never break that button or have it quit functioning) Once you free this area you have successfully removed glass and digitizer for replacement.
Some more sides notes to keep in mind there is quite a bit of electronics in the speaker and home button areas so be very careful when removing the glass and before you seal anything back up dry fit it and test it out to make sure that you haven't cut or damaged anything so that you can save yourself a lot time and frustration now. Also the digitizer is glued/taped to the glass so if you buy one of the cheap $20 glass replacements on ebay it isn't going to include the digitizer so make sure you get what you need. It took me about 20 - 30 minutes to free the screen from the plastic housing. One last thing, I am not an expert on the iphone by any means but there seemed to be some sensors of some kind in the speaker area and I noticed that there was no glue residue around these areas on either the plastic housing or the glass area so make sure that when you reattach the new screen and digitizer not to cover up anything that wasn't covered up before because things might not work right if you do. Good luck
1: The first minor issue I came into was when I went to pop the screen off to open it up. By the way I took this apart with the tiny screwdrivers you get at the real dollar stores and box cutter knife
That said I highly recommend getting one of those blue pry tools as they make life a lot easier. When taking the screen out I had to "rewind" the video a few times to try to catch where they were prying this apart. so here is a picture to help better illustrate how to get this thing apart after removing the two screws:
2: I don't have pictures of this but as a side note when I tried to pop the lcd away from the digitizer it was flexing quite a bit and wouldn't let go! What I did was run the knife between the two metal brackets you just unscrewed and popped one side off at a time; it came off pretty quick and easy when I did it this way.
3: This was where most videos and info went cold...I guess the screen just magically fits on at this point lol. What I did here was follow the info from ifixit and heated the sides first to free the sides of the plastic frame from the glass screen and digitizer. This gave me a point at which I could continue to work the screen away from the housing and it came off pretty easy. Next I spent quite a bit of time slowly heating and prying the speaker area away fromt the plastic housing. This is held on with double sided tape and after heating I carefully used a knife to help free it. Next I pryed the home button area free using the same method...if you happened to need to replace the home button you are all set to do so now. (Wow hope I never break that button or have it quit functioning) Once you free this area you have successfully removed glass and digitizer for replacement.
Some more sides notes to keep in mind there is quite a bit of electronics in the speaker and home button areas so be very careful when removing the glass and before you seal anything back up dry fit it and test it out to make sure that you haven't cut or damaged anything so that you can save yourself a lot time and frustration now. Also the digitizer is glued/taped to the glass so if you buy one of the cheap $20 glass replacements on ebay it isn't going to include the digitizer so make sure you get what you need. It took me about 20 - 30 minutes to free the screen from the plastic housing. One last thing, I am not an expert on the iphone by any means but there seemed to be some sensors of some kind in the speaker area and I noticed that there was no glue residue around these areas on either the plastic housing or the glass area so make sure that when you reattach the new screen and digitizer not to cover up anything that wasn't covered up before because things might not work right if you do. Good luck