I bought the iFixit kit which included the battery and the tools needed to replace it (replacement adhesive pads, screen opening picks, etc.). I was successful, but it's not exactly an easy process. The gel pack that came with the kit, which you are supposed to microwave to heat up and use to melt the screen's adhesive, didn't do anything. Instead, I had to use a hairdryer (a heat gun would work as well). Other than that, following the iFixit guide worked perfectly for me. Really do be careful when cleaning the old adhesive off of the display, as it's very easy for whatever you're using to scrape it off to slip, and you will almost certainly damage the display if you drag the scraper over it.