Zeffer, when you look at parts from South of the border INSIST on them being sent by USPS, not UPS, FedEX, Purolator or any other Courier. Couriers have a nasty habit of F*****G you over for brokerage fees. The fees can sometimes equal or exceed the original cost of the item.
You can always ask the sender to clearly state "Warranty Return" for the item on the package, this will usually avoid any taxes or duties.
Bigger companies may or may not do it, but it cost nothing to ask.
Individuals that you purchase stuff from on eBay may do this too.
What ever you choose to do, good luck, but remember, STAY AWAY FROM THE EVIL COURIERS, they are vile, corrupt, and not very nice people!