5 - 30 minuten
My iPhone 4 lost all battery power, couldn't charge, so i couldn't turn it on. Took it into an Apple store and they told me it was "probably" the battery. And that would cost almost what the phone was worth right now to replace the battery.
So I decided to look online to see if it was possible for me to replace the battery and i found iFixit. Looked at the site and how inexpensive it was to get a battery and the tools to do my own repair. Ordered the same day i saw the site, got the kit a couple days later. So after watching the iFixit battery replacement video, BAM, within 10 minutes my iPhone charged up and no problems at all. New life for my iPhone 4. And the two screw drivers, extra screws, plastic pry tool made it incredible easy to do the job, nothing else required. Couldn't be happier with my purchase and the help this site provided. Saved me money and/or just scrapping the phone altogether.
i guess the only advice i would give is do the repair on a large white surface so you don't lose the screws or parts when you open the phone, cause the screws are very small. Even though you have replacement screws in the kit, just makes it easier to see the tiny things if you do it on the right kind of table with enough lighting.