Changing the phone is easy. All you have to do is take the SIM car from your old phone and put it in your new phone. If your new phone takes a different size of SIM card, you must purchase the correct one ($10+tax). If you buy the iPhone from Koodo, you should get the SIM card for free. You can change the active SIM yourself via Self Serve.
If you want data, you'll have to change your plan, as there are no data add-ons to choose from.