20 - 30 minutes
Replacement Iphone battery went kaput after 5 months, wouldn't charge.
Took my time. Very difficult to remove screen. Asked for help from Ifixit community. Finally got screen off. Had difficulty removing battery. Worked using the heat gun trick. Put everything back together I thought. Then realized cables 1, 2, 4, and 7 were not securely attached. Apparently they were not snapped into place but I didn't know that. Finally put the cover back on and everything worked, that is, the stuff that worked when the old battery died came back to life. Camera still doesn't work.
Your repair manual should explicitly state how to know that cables 1, 2, 4, and 7 are securely in place. I thought they were but when I re-opened the Iphone, the cables were popped out. It required lots of pressure to insure the cables would stay put.