Just to add to this since I've gotten 2 work permits and did my landing at YVR. If you will be there during normal business hours, right after passport control are all baggage claims, and to the right of those is the main immigration office. You'll grab your luggage and go over there. Right outside the office there'll be an area to leave your luggage with an airport official watching over it. Quink, I'm not sure why you waited to get your luggage until after you got your permit. Both times I got my permits, in 2013 and 2014, I got my bag first and then I went to immigration.
You'll be directed inside the office where you'll wait for someone to see you. Sometimes this can take a while, it'll depend on how many officers are working and the number of people on line. First time I went through it took me about an hour of wait time and the second time about 10 minutes. The actual landing is usually pretty quick, mine took under 10 minutes.
If you are going to be landing very early in the morning or late at night, the immigration main office might be closed. That's what happened to me. If that's the case, then after you get your luggage, instead of heading to the right, you'll head to the exit where you'll see a couple of immigration officers checking people's customs forms before they leave. Let these officers know that tou need to do your landing. They'll wave you to pass them and go to the doorway on the right, which is secondary. Then you'll wait on line until an officer frees up.
I think you'll be okay with 4 hours, but it might be close. Both times I got my permits took about 45 minutes on the passport control line before I got through the baggage. Then as I mentioned above, one had about an hour and another 10 minutes in immigration. When I did my pr landing there was not wait at passport control and about 35 minute wait in secondary.
The good news is that passport control, baggage, and immigation are literally right next to each other in one big area.