My old phone is dying and I want to replace it with a smartphone. I use a prepaid plan and I do not use my phone much. However I travel to Europe twice a year and I would like to be able to use my phone when I am there. I know I will need an unlocked phone. Should I get a used iPhone 3GS or a new $150 prepaid smartphone such as the LG Optimus One, a Samsung Galaxy Gio or a similar phone? How reliable is the 3GS? How difficult is it to unlock? Is this something I can do myself?