Cant add much to the good advice given here, except to say that I have been using my Kindle outside the US for several months, with very little problem. It will be even easier for you, given that you have a US-registered credit card.
On the issue of downloading samples, if you have an iPhone or iPod Touch, install the free Kindle app. This will let you download samples to the iPod.
My only worry would be the battery. If you need to send the Kindle back to Amazon for a replacement battery, they might need a US address to return it to. That shouldn't be a big problem, but if you feel the battery is nearing the end of its life, it might be worth getting a replacement before you leave.
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