5 - 30 minuten
I dunked the phone in water... while it was charging... for 40 minutes. It slipped into a cup of water in my car while I was charging it on a long trip - I went to take a sip of water and had a huge "Oh s#@t!" moment when I was looking at my iPhone submerged in my cup of water still plugged in to 'charge'.
I dried it for a week in rice before trying to turn it on. The phone wouldn't charge nor stay on. I could - briefly - see the home screen between on/off cycles while on a charger.
The repair went very well. My first time in an iPhone. It took 20 minutes, mostly because I was working on a Verizon iPhone and didn't know, until now, that there is a separate (and slightly easier) guide for the Verizon iPhone. I did have to clean the battery connecter on the iPhone.
I've charged it up, updated the software, added apps - it seems to be working fine!
The video, and the advice, are worth watching. The picture guide and descriptions accurate and helpful. Please note that if you have a Verizon iPhone 4, there is a separate and slightly simpler procedure than for other iPhone 4.