I would do the open work permit permit too, because it gives you implied status until they make a decision on your case. That means you can continue working until they process your OWP application, which will be after you get AIP (after 6 months).
This is the application form:
http://www.cic.gc.ca/english/information/applications/extend-worker.aspJust tick the C box for initial work permit and don't forget to mention not to have it processed until AIP is reached.