Seasons greetings to our brothers in the south. From a brother who's family first came into America from Ireland and wore both blue and grey. God bless. If you go into this website into FAQ you'll pretty well get all the answers you are looking for. Or PM one of the organizers of this site, HOJO (aka Myles).
I'm no expert and no doubt you will get many replies but You are bang on. Much more strict. Chances of carrying things across the border as a private individual or having them couriered directly are slim and none. They will be seized and destroyed. We work through retailers such as the ones listed on this site to get our AEG rifles and GBB guns. We can however get parts. But the threat of seizure is always there.
It would be great to cross the border for joint US/Canadian airsoft milsims and games. I did it for years as a Civil War Re-enactor and had a grand time. However, we had to have our repro muskets registered and all paper in order to cross into and back from the US.
Again 99% of your answers are already in this website. Look and ye shall find.
God Bless and all the best for happy and prosperous 2007.