Blast, good luck in Paris.
We’ve been there several times, most recently last summer. We traveled on the Metro all hours of the day without problems (except those 2 pickpocket attempts – unsuccessful). If you carry a Palm, a useful program for navigating the Metro is “MetrO” (available at http://www.nanika.net/metro/).

To further “pass” as a Canadian you can get a “Canadian” passport cover, actually any country, that will pass casual scrutiny.

Having a pocket phrasebook can help. I think mine is a Lonely Planet version (on loan), it’s more practically oriented than most phrasebooks.