Replacing heater core in my 1991 Ford Thunderbird with air conditioning

Well, it was loads of fun. I did not take out the heater box. I did not disconnect the air conditioner, because I didn't want to have to refill it. I had everything loose and tore the rubber gasket (that can't possibly be taken off any other way) from the heater core input/output lines that come off the heater core like a V. I replaced the core and put it almost all back together including the ripped gasket. Looks like I had a few extra screws and a insulation sheet that probably went somewhere between the heater core and the radio. Everything seems to be fine. Following any directions from my Chilton manual was an exercise in futility as it covered 15 years of Cougar and TBird with no real explanation or diagrams from my year. Warm in time for winter and a working defroster. Thanks for your comments.

You need to evacuate the refridgerant and disconnect the A/C lines to go any further.