The application must be filled out using the name that is on your passport or travel documents - so, if that's your maiden name, use it and submit a copy of your existing passport or travel docs with the application. Then make arrangements to get your name changed on your passport - and, once you receive the new passport, update CIC with a photocopy of that. Your marriage licence references both names (and sometimes even makes note of the fact that you're taking your husband's name) - so there is no need to worry that they somehow won't believe you're married just because your names are different.
The important thing is that, if you are applying inland, you need to get the entire application - as well as
the extension application for your work permit - submitted to CPC-Vegreville so that it's received BEFORE your status expires. Track the mailing and get delivery confirmation. Once that's done, there's time to update your name change. Keep in mind, though, that you can't leave Canada during inland processing - so if you have to present your passport in person in order to get your name changed, you're going to have to wait until after you get PR. That means your PR (and PR card) will be issued in your maiden name, and you'll have to apply for a new PR card, with your new name, once you get everything sorted out with the passport.
