At this stage I found you do not need to do most of the rest of this guide although it does come with a warning. The battery is tethered to a metal ring which is the base of the retention screw in step 29. After Step 33, you can separate out the batteries from its adhesive now with a blow dryer or the iOpener (step 56). You will then find the battery free but hooked onto the ring. Take the blue opening tool (see step 55 for which tool this is) and wedge it where the battery is to make a gap. You can then lift the battery contact from its hook. After removing the battery, insert the new one into the small gap created by the wedge. The caveat is that you are bending the logic board a bit with the wedge so use this technique at your discretion.