How do I repair/replace the heater core and should the compressor be prlced also on 1996 Dodge Grand Caravan

water runs into the cabin of the vehicle and the windows steam up. Is this a result of a faulty heater core

Windows steam up, now that sounds like a heater core problem. Tip, antifreeze taste sweet! A little tiny bit wont hurt you either.
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Are you losing coolant, or is it water condensation from A/C unit not draining properly?