I shipped some drum pedals to Canada... they got delayed in customs by a couple of weeks and the buyer raised hell with me, even though I had a receipt and insurance.
Make sure the guy you're shipping to know that there could be holdups. Get proof of shipping, and make sure he pays all the fees. Other than that, you should be good to go.
I get a lot of items shipped from the states. If possible ship it USPS. FedEx and UPS charge a brokerage fee that is usually as much or more then the actual shipping. There is a little extra paperwork but it will only take a extra minute or two to fill out any way you decide to ship.
I've gotten parts from guys in the US too. Please do the buyer a favour by shipping USPS if possible will save around $70 in brokerage fees charged by pus and fedex
USPS is the best for shipping from the US to Canada. The Brokerage charges by UPS and the like kill us. Make sure you list "used" in the description of the item.