There is a fair amount of misinformation in this thread.
OP, read over this appeal to get a feel for the laws. It's pretty much identical to your situation.
You're going to need to prove that the body kit is a part designed for a firearm and not a replica firearm. It's going to take a lot of work and take a long time and even then I am not sure you will win. They're going to want to see that the body kit is for the Canadian Version of the TM 226. Proof of the item being available in Canada is not acceptable and they will not even take it into consideration.
When you get your notice of seizure it will explain how to export the product. That's the return to sender option and you will have to arrange that yourself. If you do not arrange for exportation I believe they will destroy it.
Feel free to PM me if you have any questions.