Been a while since I've lived in Vancouver, but I can tell you this:

- There's a good hotel at the airport, in the international terminal. Probably not cheap, but very convenient (and the bar has an excellent selection of Scotch if that's to your liking). Google it.
- There's good long-term parking not far from the terminal. Follow signage from Hwy 99 to the airport, then look for the parking lots on your right as you approach the terminal. They run a shuttle. Rate might be CDN$12 per day now??? I'm guessing, maybe someone else can advise.
- CX has a first & business class check-in desk on the outside wall of the international terminal, facing the main check-in area. Last time I went through there, about a year ago, the process was very efficient and so there should be no reason to show up 3 hrs early. If you stay at the airport hotel you can check with them the night before as the desk will be open for the night flight that CX runs (or used to run, it's been a while!) to HKG.

Service is good on CX so enjoy your flight!