Take with you all the visa related documents/status adjustment documents (old and new/current - all I-94). Generally you don't need to get a new visa in Canada, although the officers at the border will ask you why not get a new visa, you can tell them that you cannot make an appointment for an approperiate date and you can promise you will get a new visa next time. This is only my experience - I am a H1 holder and already had twice round trips between Vancouver and Bay Area. I will go to Vancouver again in December, but this time I am going to get a H1 visa - On my passport, the visa is still F instead of H.
Good Luck!
Good Luck!