I've installed basic security monitoring systems before. Nothing elaborate but would do the trick. If I lived in Calgary I'd offer a hand if you didn't need/want a professional.
If you want to fly me out I'd certainly do it for free
That said, I'm not familiar with the particular Costco system, but in terms of doing it yourself the things you want to cover are:
1. Cash register
2. Entrance
3. Expensive Items
4. As much of the floor space as possible.
Depending on your staff, one in the back room as well.
In terms of running cable, it sounds like the most daunting, but if it's drop ceiling go to the Source, get a monster truck (not just any remote car but a monster truck) and then tie the cable to the truck and use the truck to run the cable where you need it to go.
The rest is likely plug and play.
If you have any questions, I'll try and answer them. Feel free to send me a PM.