Oh- you are from the USA.
Your "international " buyer is Canadian then? You are on the eBayCANADA site.
Basically the same advice holds. Do use the postal system because UPS charges an amazing amount to clear the border on any parcel valued over $20.
If you sold it, it is not a gift. And even gifts are dutiable (Hey, we have to finance that universal health care somehow, eh?)
Rates to Canada (and Mexico) are lower than rates to overseas. Check on USPS.com
Usually First Class International is acceptable, but if you feel really nervous, you can insist that the shipping be by Global Priority and that starts somewhere around $20-25USD. There are lower similar services but they are not Delivery Confirmed.