I don't recommend using this module, since it's not being updated and since it's an unnecessary Frankenstein-mix of the following two modules:
CanadaPost Shipping Module for showing your customers all available options and rates
Canada Post Automated Labels for generating shipping labels in your backend
It's better to use those directly as they are more recent and each is updated at its own pace.
If you want to also ship Canada Post Light Packets Air, you can do so via the PayPal Automated Labels module, as this is not available directly though Canada Post website.
If your shipping rates with Canada Post aren't great, you could use eShipper Integration Module in your backend for better rates when generating labels (this applies to Regular, Expedited, Xpresspost and Priority). Try eShipper quotes first to see if their rates are better.
If starting from scratch, I would probably go with the free Magento eCommerce solution. osCommerce is too dated...