AC Heater Core Replacement tips????

[kxnomore]

As luck would have it, I just installed all new AC diverter box, hoses, glove box, AC Control assembly, cables, radio, center vents, etc, and on the first drive my Heater Core started leaking!

I've read all about how to change out the normal heater cores, but I've heard the AC ones are totally different. Do you go at it from the inside and not the outside? Any tips would be greatly appreciated, as I'm running up the natural gas bill getting ready to stick my head in the oven... Just kidding.