Call the CFO with all yours and the buyers info, including Pal #'s etc and all the gun info including serial number and the registration number you were issued for it. If you still have your book from the pal course, it lists it all near the back in appendix K.
Their number is 1-800-731-4000
The best way to ship would be in the original box and Canada Post has the best rates, make sure its signature required & insured. When canada post was on strike i checked the other outfits, and they were all substantially more expensive and most have additional fees for firearms if they ship them at all.