Just the first month being played isn't too bad, but I have seen new copies on sale sometimes for ~$50. Though not sure what the options are for Canada (you may be more limited).
Not sure if there is any point in replaying the January scenario; you will see the stickers that resulted from the scenario, and you may play differently because of knowing what the result is. You could just keep going though to the next game (February).
Depends on how much a new copy would cost you. Replaying the first month would not be excessively hard, but it's also not ideal (it'll be a bit messy, you may want to apply some key stickers in different places, and you'll have your initial surprises spoiled for you).
If a new copy costs $60 and you can afford the difference, avoid this used copy. If a new copy costs $150, the impact of the first month being played probably won't be so devastating as to be worth paying three times the price.