It sounds suspiciously to me like you have a broken heater core. (It's located just under the dash above the passenger side.) I don't know about a 97Ranger, but in the earlier Rangers, replacing a heater core takes about 20 minutes -- with no taking apart the dash. (I've had two heaters go in the 12 years I've owned my Ranger.) Of course, you should also flush the cooling system after wards if it hasn't been done in a while, in case the old coolant had something to do with the break down. New heater cores -- at least on my 88 Ranger, I don't know about the 97 model -- should cost no more than $150. If I were you, I would find a Haynes or another similar manual and read up on it to see what's involved. It might be something you can do yourself.