As of today, my passport is valid until July 31, 2012. And I've got all my CEC documents ready.
Should I go ahead and submit the application?
or Should I renew my passport first?
And my work permit is valid until July 31, 2013, Will my passport renewal affect my work permit? (such as different passport number, etc?)
Note: I'm holding British Passport, only ID is required to send for renewing passport, so I can keep my passport with me during the process.
You can submit your application if it is ready.
As for your work permit, PMM should answer this, but I think you're OK, I would just advise carrying both (new and expired) passports when entering/exiting Canada.