Yeah, update to the latest firmware via iTunes (3.1.2) - then download blackra1n from here;
www.blackra1n.com - download it, click 'make it ra1n', wait 15 seconds, your phone will reboot.
Once the phone has rebooted go to your iPhone homescreens, click 'blackra1n', then install 'Cydia' and 'Blacksn0w', wait for the phone to reboot and the phone will be FULLY unlocked to ALL networks. Then just go into 'blackra1n' and click 'uninstall blackra1n', to make the icon disappear as you won't need it anymore. Done. :)
Hope I helped. :P
And yes, it really is that simple.