Heater core problem, Ford Expedition. Need advise?

My 2001 ford expedition is having problems. My windows fog up and there's a sweet smoke smell that is coming through the vents that is making me sick. It is not constant but it is a real problem. It is going to cost $700 to have a mechanic repair. Is there anyway to bypass or stop the air that comes from the engine to the cab? I heard that i can use a clam to plug the two hoses that goes into the cab, which would prevent the water/antifreeze going to the heater core. Will that cause problems?

You can do that but you won't have heat in the cabin. Find the money and repair the heater core or get a new or newer car.