The best option is to go at a store, because you will need a new sim card, wich is free with the activation. Bring your Koodo account number to easily transfer your phone number from there.
With the new financing structure, you will have to pay the balance in full. It is possible, when you buy the phone, to choose wich type of financing you prefer, but it can not be changed later.
You only have to call the Customer service (*611) and ask to convert your account into a consumer account. You will loose the discount for the next months since your no longer an employee, but you discount for this month should not be removed.
The credit verification is made before the activation, so before you have to pay. If something goes wrong, you might have to pay a deposit or to choose have credit limit on you account.