2 - 5 minutos
Thanks to Uncle Steve's crazy penchant for secrecy, no iPhone 4 cases were available from reputable manufacturers until 6-8 weeks after its release. In the meantime, my all-glass-exterior device which is intended to be held in the hands very frequently fell on some concrete while I was walking the dog, and the bottom of the back glass was shattered. I thought I had to live with it for 2 years until I upgraded to a new phone... but iFixit to the rescue! Now I can take my phone out of the case to clean it without being afraid it will completely fall apart.
Incredibly easy. Took 2 minutes.
Wait to buy fragile devices until cases are available. And maybe let Uncle Steve know that now that his market cap is pretty much tied with Exxon Mobile as the biggest in the world... maybe meeting the needs of the installed user base is a little more important than developing in absolute secrecy so you can make a big splash in the media.