Apple How do i unlock iPhone 3G 8 GB. 4.2.1

[tagzard]

So my uncle is moving to mexico and he wants me to unlock his iPhone 3G 4.2.1 8 Gigs. So how do i do this. And if possible can i unlock a iPad 2 3G. But the iPhone is a priority.
His badeband or Modem Firmware is 05.15.04

Also he already has a AT&T sim card but he won't use it anymore. So should I take the card out?

 

[Dialexio]

The iPad 2 (GSM model) already ships unlocked.

The iPhone 3G can be unlocked with redsn0w. On the options screen, only check off "Install iPad baseband." Please beware that this is a (currently) irreversible process, and may cause issues (malfunctioning GPS and the inability to use Apple's IPSWs).

As for the AT&T SIM card, I would keep it out (though leaving it in should do no harm, provided the account was canceled). However, you will need the SIM card to restore in iTunes.