New Rear Camera for iPhone 4S -- saved me from buying a new phone!
30 Minuten - 2 Stunden
My iPhone 4S's rear camera was having problems auto-focusing. On 75% of shots it would not come into sharp focus, I had to repeatedly tap the phone against my palm, re-compose the shot, etc. A real pain since I need to take pictures for work purposes often.
Using iFixit's repair guide I was able to disassemble, replace the rear camera module, and reassemble in under 20 minutes. (I had previous experience replacing the battery in the phone so I was familiar with the basic procedures.)
This repair, at ~$38 incl. tax and ship, was worth the time and trouble. Highly recommended.
Pay special attention to the new camera module's lens when installing. Before you put the rear cover back on, use a quick, light burst of dry compressed air to blow any lint or dust off.
Also, while the rear cover is off, use camera-lens cleaning liquid and a lint-free cloth to clean the *inside* of the rear camera lens cover glass. To be clear: do NOT use any liquids on the camera lens itself -- only on the **protective glass** on the inside surface of the iPhone's rear cover. Let it dry completely, upside down so no more lint or dust falls in it, before putting the cover back on the phone.