Travel to Canada with Green Card

I am a US permanent resident and have no other passport for travel.
I need to fly to Toronto for one week in a
business trip.
Do I need a travel document or for Canada my green card is enough?
I prefer not to apply for reentry permit because soon, end of April, I will get the US Citizenship.
Also, in Canada will I be able to rent a car
with my CA driver license?
Thank you
Mike D.