heater core leak pools under carpet in rear?

My step-son's 97 A4 quattro (V6) was losing coolant badly a few months ago, so we parked it for the winter. Trying to diagnose it now... I refilled it, put the front up on ramps to help bleed out the air, and it seemed to stabilize. But then I noticed that coolant is pooling in the rear seat footwell on the passenger side. I do see a small drip under the dash in the glovebox area also. Does it make sense that a heater core leak could be causing this? Also, how much of a chore is it to replace it, I assume some major instrument panel dis-assembly is needed?