How to replace a heater core on a 94 Lincoln mark8?

The heater box was preassembled and shipped to the Lincoln plant for assembly. The box is installed as a unit then the dashboard is installed...... Get the picture? You have to take the dashboard out and disassemble the heater box to get the job done. I advise a trip to your local library for instructions for your needs first! Not much else to say... Good luck!