10 - 30 minutes
I had messed up the headphone jack trying to get lint out of it, but I was just living with it. Then the back of my phone was cracked open, and I pulled it off to verify that my battery had begun the li-ion battery's swan song of expanding, so the repair couldn't wait any longer.
I'll be honest, that was almost as scary as dropping my transmission for the first time. Thankfully you're guides are excellent and your pictures contain many pixels, so I made it through successfully.
Don't be too scared, but don't get sloppy, either. Also don't toss the parts you're replacing immediately. I probably wouldn't have been able to fold the headphone cable up properly if it hadn't been for having the old one sitting there.