you submit work permit and TRV renewals to CPC Vegreville, AB but I believe you have to attach your nomination certificate to the application although you may want to check CIC's website first because I might not be 100% accurate.
http://www.cic.gc.ca/english/work/extend-stay.asp
my husband's work permit is about to expire on Nov.30, he submitted his application for work permit extension on October 15. since his nomination is already apporved and our application for PR is already in process, he only attached a copy of the nomination certificate.
in some other situations, you will be required to submit a new LMO together with the WP and TRV application.