Your best answer for that would probably be your current provider. You will need to work with them to help get everything set up for your travel and when you get there in any case and they usually will be helping with figuring out billing.
Even if it doesn't answer your exact question, there is a post on page 2 of the disABILITIES FAQs thread that should answer any other things you think about. If it doesnt, please feel free to ask - there should be posters who traveled with oxygen around this board.