If you really don't want to get a work permit, you should apply to change your status to visitor but if you do that, you should not work once your work permit expires. Do not take the chance of working illegally. You can give your reason for changing to visit visa anything you want but waiting for PR is as good as anything else. Just write that if you are called for an interview in Korea, you will have to go there so you will not overstay. However, you might not even have an answer on your visit status by the time you get the PR because it right now takes 103 days to process, see
http://www.cic.gc.ca/english/information/times/canada/process-in.asp#temp_res You should still apply for it though, just because it's the right thing to do.
Once you have the PR, you can work. If you have it processed through Korea, it should take 3 to 5 months, see
http://www.cic.gc.ca/english/information/times/international/05-fc-spouses.asp#asia but the processing in Korea doesn't start until you have been approved in Mississauga which takes right now 32 days, see
http://www.cic.gc.ca/english/information/times/canada/process-in.asp#sponsorshipYour total processing time it therefore something like 4-6 months so if you apply in December, you would probably have your PR between April and June.