Student Visa/Residence Permit

Hello,

I would like to inquire about the visa/residence permit for foreigners in Belgium. I am a Canadian citizen and I have a student permit here in Belgium. However, my permit expires on December 31, 2018, but I won't be able to leave Belgium before January 2019. What is the implication then? Would I be allowed a leniency period of, say, 1-2 weeks to sort myself in preparation to leave? Also, as a Canadian citizen, who is granted 90 days visa free (as a tourist) to any Schengen area, would my residency permit automatically change to a tourist status, or will I need to do something at the commune and/or leave the Schengen area and come back as a tourist?

Appreciate any information you can provide.

Thank you.