I don't know, but when my blower motor stopped working I debugged the wiring and found a problem and fixed it. Fortunately, this saved me from having to work on that cage assembly on the passenger side firewall. Perhaps you've just got an electrical problem that might be fixeable?
For A/C equipped machines you've got a big job ahead of you. Search Projectbronco.com to find some good info on that job. A Chilton's or Haynes manual won't be any help because they tell you it's too complex for the home mechanic. I tossed the whole AC unit and converted to the standard heater.