I'm assuming the gun is registered? If not, don't sell it here. Register it first.
Work out the deal with the buyer, call the CFC and give them the Reg. Cert. number of the firearm being sold. They will validate all your info, and the serial number on the gun. They will ask for the PAL # and name of the buyer. They give you a reference number. Give the reference number to the buyer, they will call the CFC and complete the transfer. Once it goes through, you can ship the rifle.
If you're wanting to sell a Garand - send me a PM and tell me how much- I've been looking for one for a while!