15 minuten - 1 uur
My iPhone 5 was a hand me down from my Dad and he used it for work so the battery was completely drained by the time I got it. I had to charge it several times a day and had to carry a charger with me wherever I went. It was a disaster of a phone!
The only trouble I had was getting the screen off. I would suggest buying the whole kit if you don't have one of the suckers that comes with the whole kit. Fortunately, I had one and a friend who had a little more strength than I did. He prized it off and after that, replacing the battery was a piece of cake! The original battery was help down really, really well with double sided tape, but again, I got it off and put the new one in. Now it's an absolute dream. With fairly regular use, I get a full day out of the battery now. Like the title say, absolute life saver!
Like I said, I'd buy the whole kit if you don't have the sucker to get the screen off. Apart from that, just be careful with the screws and taking the old battery out. It's so easy to puncture batteries so try not to be too heavy handed with it.