iPhone 3G/3Gs Screen Repair Procedure 
Disclaimer: Opening the case will void the manufacture warranty. TopTechies is not responsible for damage or problems that may result from following the disassembly and replacement procedures.
Preperation:Start with a clean, open table that has good light. Prepare all required tools and parts required for the repair. Make note if you've had issues with static electricity in the environemnt. If yes, you may want to use a static wrist band or ground yourself prior to starting disassembly.
Required Tools: #00 phillips screwdriver, flat head screwdriver, tweezers, double sided tape & small paper clip
Step #1 - Power Off iPhone
Hold down the power button for 5 seconds and shut down.
Step #2 - Remove 2 Base Screws
The screws are located near the speaker and microphone ports on the iPhone. After removing the screws set them aside in a safe area.
Step #3 - Remove SIM Card
The SIM card is located at top of the iPhone. Use a paper clip or stick pin to unlock it. Look for a small hole to insert the paper clip in order to eject the card and holder. Set the card and holder aside in a safe area.
Step #4 - Remove Glass Touchpad
a. The glass touchpad can now be lifted starting on the side that contained the screws. Use the case opening tool to wedge the glass out. The silver rim should stay with plastic backside as the glass is lifted. Also, if it's too tight a suction cup can be used to pull the glass up. Note: This is a tight fit and it can take some time to seperate the glass. Lift the glass about 3/4 of the way until you can access the ribbon connectors along the back side.
b. Disconnect connectors #1 and #2 by lifting gently with your fingers or leverage with the plastic case tool. The third and last connection is hidden under the ribbon of connector #2 (See next step).
c. Disconnect connector #3 by moving the small, black or white tab up at a 45 degree angle then the ribbon should pull free. This is the most difficult connector to reconnect as the device is reassembled. The iPhone screen should now be free and ready to be worked on to change the glass.
Step #5 - Replace Digitizer\Glass
a. Remove 6 screws located on the screen glass assembly. There are 5 screws on the side rails: 3 on the side with the flaps and 2 on the other side. The 6th screw is in the top right. There is black tape over some of the screws in this step. (The black tape is not needed so if it is causing you problems when putting the phone back together later, you can cut it off.)
b. Separate the LCD screen from the glass. Put your flat head screwdriver or a wedging tool in between the rails and wedge the inner piece out. Don’t be afraid to apply a little pressure as the metal will not get deformed. This step will free the LCD screen from the metal frame.
c. Clean the metal frame from the broken glass. This step may take a while but make sure it is done well so the new screen fits snug. The glass will come out easy as it is broken and if there is some resistance, don’t be scared to use force as long as you are not greatly bending the metal frame because you will reuse it. Use the wedging device to scrap away stuck pieces of glass and leftover residue of the former adhesive. A heat gun or dryer can be used to loosen the glue but simply scraping it may work fine. The heat gun or dryer can also cause the reusable piece to become somewhat deformed.
d. Prepare your new screen. If you have double sided tape, make sure it is cut out correctly. If you have super glue, make sure when applying it that you do not apply too close to the home button. Only apply adhesive, whichever one it may be, to the wide black plastic on the bottom or top, staying away from the middle. You don’t want to glue the home button or the listening piece on the top. Let adhesive set for a few minutes to make sure it is set.
Step #6 - Reassemble the iPhone
a. Start reassembling your iPhone. Put the LCD and glass back together. There are two ways the screen can go and only one is correct. On one side, the rail is longer than the other, so that's a quick way to match it. You may find it easier to slide the LCD in from the bottom so the little clamp slides on nicely.
b. Complete the reassembly of the iPhone. Don't forget to lock down connector #3 when re-installing the touchscreen glass. If necessary, use a tweezers to slide the ribbon into the connector.
