Re: My Heater Core is Blown !!!
I haven't seen it here, but if you serarch for "Blend Door" issues with dual zone there will be a write up on it. It's one of the things that's recommended to be changed while you're tackling this. Since the dash will be removed.
There is a lot involved, but it is do-able if you have the willingness to try, and learn. Sorry I'm not more help.