15 minutes - 1 heure
My iPhone was getting to 20% battery or less, and then dying like the battery was dead. Plug it in, and it would come to life at the smae battery % as when it shut off. Apple tested it, and the battery looked real good. We did a complete re-flash and hard reset, but the problem persisted. Checked it again a few weeks later and the battery health had deteriorated quite a lot. Battery replacement was the cheapest option.
The mildly terrifying part: pulling on that suction cup. I mean, I'm no 98lb weakling, and I was pulling with pretty much everything I had with no obvious result. I thought either I'd break the glass or rip the wires when the thing finally exploded on me. But, I kept a steady pull and eventually (probably around 4-5 minutes later) a corner started to lift and I could get the separating tool in. Once that was done, it was pretty straightforward, almost exactly like the guide. Total time: 15 minutes.
Each connector has a small foam pad glued to the back of it. They overlap and end up glued to each other. Just be careful when prying them up, and make sure to separate them before trying to reconnect.