How do you replace a heater core on a 1994 Ford Taurus after you take apart the dash and remove the bolts from the firewall?

The AC has to be dischared, and the AC lines have to be removed at the firewall. The AC drier has to be remved, because there are nuts on the outside of the firewall under the hood to remove that are hidden by the drier. I believe there are 4 nuts to remove, but there might only be three.