I had waterfall noise for few months, now windows fogged up and started smokin when I pulled carpet back. I know it's heater core just wanted to double check it is for sure and if anyone has suggestions to make it easier.

 

The noise you heard is the water circulating through the heater core. Not sure about smoking though. If windshield is fogging from moisture, it's probably a leaking core. You should be smelling that antifreeze pretty strongly inside the cabin if it's leaking.

 

Had the same effect on my Blazer when the heater core went, like a fog coning out of the vents, think the hot water comes out in a fine spray then condenses in the cold air. When it happened on mine I really thought the truck was on fire, the whole passenger compartment steamed up.