Will I be able to use my iPhone from Canada (rogers) in China? Probably on the

[RemiMartin]

China Mobile network SIM card? I'm moving to China next year and I have an iPhone 3G that I currently have with the Roger's network in Canada. When I lived in China before I was able to bring my phone that I bought there back to Canada and use it on the Rogers network. I'm wondering if I will be able to do the reverse? Take a phone (iPhone) purchased in Canada and use it in China? Or will it have to be unlocked or something like that? I didn't have to do anything special to make the phone that I bought in China work in Canada on the Roger's network.
also, if it will work in China, can I use the GPS over there? and will it be in English? (any ideas??)