Hello!

Newbie here. I noticed there is a way to download maps to cell phones and use them to run the navigation programs. Is there a way to do the same thing with a US spec iPhone 3Gsi? I bought an unlocked one hoping to be able use in Korea but to only find out that the only phone that will work here is the one you buy in country. But since I have the GPS capability, could I be able to do the same thing with the right app and will it work with out a cell phone service?