Taurus that blows

I have a 95 ford taurus. My air conditioning/heat only blows on high. Also, when I switch from heat to air, it will stay on heat. Eventually–after a number of weeks, it will eventually blow cool again.

How extensive is tjhis repair?

Find out where your fan resistor is. It’s burned out. You’re bypassing it on HIGH speed. Your other problem would probably be unrelated, but sounds like a function of the switch mechanism. It’s usually an integrated unit that controls both temp and door actuation. $$$