[RJ911SC]

How are you going to ship? Truck lines?
you will need to do up a commercial invoice with values,
keep a copy of the bill of lading, and the commercial invoice, for the return customs clearence. {proof of export}
on the commercial invoice, put as much info as you can.
seats being sent for repair, or re covering, should be put on the commercial invoice. take pictures before and after.
when you go to clear back into Canada show the proof of export and the invoice from the company who did the repairs, you should only pay on the work done and not on the value of the seats prior to having the work done.

good luck

79 911SC
09 mini Copper S
10 Kia Soul 4U SX