I had a cracked screen and the proximity sensor was not working. I was constantly getting cut off from phone calls that I received as well as phone calls that I made because my face would come in contact with the phone's screen and end the phone call. Not to mention the phone looked wrecked with a cracked screen. I decided enough is enough of this status quo and was determined to get it fixed.
I purchased the iPhone 3GS Front Panel Assembly, followed the online instructions and presto, iPhone is fixed. It took less than 30 minutes to remove the screws, screen and then reassemble. I did it with tools that I already had in my household without having to buy any tools. I already had the small phillips head screw driver that I had on a key chain I had received as a gift from someone and I suppose if you had a small repair kit for eye glasses that you can buy from Walmart, the small phillips head screw driver in the repair kit would work just as well. I used a small wooden shish kabob stick as my tool of choice to lift the locking tab for cable number 3 and that was it. No problems encountered, everything went smoothly.
If you need your cracked screen or proximity sensor fixed this is the way to go. I highly recommend the 3GS Front Panel Assembly. It is quick and easy with no complications. Just follow the online instructions and enjoy your new iPhone.