Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
Tough to answer your second question without knowing what coverage -- if any -- is already provided by the rental-car company. Do rentals originating in Canada include third-party liability coverage? If so, how much? Do you have any private insurance that covers you for third-party liability when driving a rental car?
As for damage to the rental car itself, does any of your cards provide primary coverage? Check with your card issuers, or review the card-benefits brochure that should have been sent to you by the issuer.