IMHO: The best way to send it back to the dealer is using USPS Exress service and eventhough the shipping cost is high (about $33 from the eastcoast if I remember correctly) you have a piece of mind knowing where it is using the tracking number and the dealer can't deny of not getting it. I have done that a few times without any problems. Sometime you can work with the dealer about the shipping cost.
Another fellow Vietnamese, welcome.