Hey Habibti,
Congrats on making it to the end! I understand that it is a big step for your husband and I hope all will go well, but I'm sure he will be fine! also because all borders officers are bilingual, so if he is more comfortable in french than english for example, then he will be able to get help in french as well - and given that he is going through Montreal, quite a few people should be able to speak french there too...
Once he gets off the plane, he will be (with everybody else) going through border control. When he gets to the officer, he has to tell that he wants to "land as a PR" but it will be pretty obvious from his type of visa. He will most likely be taken aside to another room, where he will be asked a couple of questions - is he still married, is the information on the COPR correct, what will his address be in Canada (because the PR card will be sent there directly), and he will be ask to put his initials in 2 or 3 places on the COPR, and sign it in front of the officer. - do not have him sign anything before he gets there!
Sometimes the officer will take time to explain the basics of PR ( how to maintain the residency, the obligations), some border controls have a "welcome to canada package" with info in SIN etc, but you can do without... once he has signed - welcome to Canada, he is officially a PR!
if he is bringing goods into the country, make sure he has with him the B4 list to be stamped at the same time as landing ( if he is bringing 2 suitcases of clothes and nothing else, then he probably doesn't need it, but in case, just have it ready. if he has "goods to follow" then it's important to declare it them, and ask for papers to be stamped).
Most likely he will be then escorted back into the "normal line" and he will follow through with procedure - clearing customs for his own luggage, and then going on checking them back again ( usually it's no worries as a lot of people are doing the same... he just has to follow "connecting flights" and there will be agents along the way to guide him), and going to his gate to Vancouver.
Good luck with the landing, I'm sure it will go fine, for most people it's a really easy and nice experience!
nothing to be stressed about.
Merry Christmas!
Sweden