10 - 30 minuten
Battery went from 30% charge to nothing in a few minutes. Battery life reduced to about 3 hours.
It took about 20 minutes but this was a first time, so I was VERY slow and careful. I backed up my phone to the computer - full back up. I washed my hands well before the procedure to minimize transfer of skin oil. (You have about 10 minutes before you should wash hands again if you are concerned about skin oil.)
I had jewelers forceps from my days as an electron microscopist, so they were useful for picking screws up. I placed the phone on a lint free cloth in a tray to keep parts from getting lost. The adhesive on the battery was very sticky so I had to use the plastic lifter tool to sever the cords of glue, lifting the battery from the right side and opening it like turning the page of a book. (I did not use the pull tab at all.) Reinstallation was a breeze, but I took care to fold the battery connection so it fit snugly next to the battery out of the way of the circuit board connection at the lower left corner. The antenna connection was easy to put back. I did this with forceps. The only time I needed to use a finger was to gently push the connector so it snapped onto the contacts before reinstalling the screws. I cleaned wherever I touched with rubbing alcohol and a cotton swab. I bent the antenna contact ever so slightly upward to improve the connection with back of the phone and cleaned it and the back of at the phone with rubbing alcohol. I allowed the alcohol to evaporate for a few minutes and installed the back cover. The first thing I did, before switching on the phone was to reconnect the phone to my computer. To my surprise, the cellular reception was BETTER than before and the phone worked great. It displayed searching for a while even though I could make phone calls. I turned the phone off and on again and the reception bars returned as normal. The IFIXIT photos and video were VERY helpful. I referred to both during the process.
No additional advice. The tutorials are all I needed. Repair details above...