(Dirty Harry voice) Ok Punk. Just look up in the upper right hand corner of THIS PAGE. Click on the button that says "Tech Articles". Follow that to an article posted in 1998 titled "Heater core removal". It's all there.

(Normal Voice) Seriously, it's all there. AND following those instructions you can R&R a heater core and blower motor in less than a couple of hours. AND YOU DON'T HAVE TO VENT THE AC!!!!!. Done it twice myself.