Hey Bibace,
I've been living in Canada for 8 years, and whenever I've had a work permit, it was always with the temporary SIN. In my opinion it is hard to find a "good job" with a temporary SIN, since people do prefer to train people they know will stay with the company for a while. It might be a bit different this time, since you are applying for PR and are on the way to (hopefully) stay in the country for a much longer time. I'll keep my fingers crossed for you anyway!
My inland application is also processing, but I have not applied for the work permit you can get while waiting. Is there a specific procedure, or is it just a normal work permit application where you tell them that your inland application is currently processing? Do I have to wait a certain amount of time after mailing off my application before I can apply for the temporary work permit? Thanks for any help!