Wet Carpet - Pass. Side?????????????

Depending upon how large the leak is, a OTC core sealant wont work. To see if one would work, you can crack a large egg into your radiator. (I know, but it really works)

Good luck, unless your car is non-ac it's a PIA to change it out. Even the method not requiring dash removal is a bugger.
 
just start takin the dash out now, not even worth playin with the snake oil people pour in thinking its going to seal all their problems. a heater core is cheap, you can get one around 50 bucks and its an easy job, just alot of crap to move from the dash