My car has been overheating

My car has been overheating. I put engine coolant and drove. Later on noticed the coolant was leaking on the ground. I took it to the dodge dealer to see what the issue was. Turns out the heater core needs to be replaced, very expensive. I heard that the main use of the core is to warm the interior of the vehicle and for defrosting the windshields, is it necessary to get the heater core replaced? Is there any way I could avoid this service?