I've got a 93' SR and the main problem is that my heater does not blow hot air out of the vents. The temperature slider is not difficult to move, it slides quite smoothly so I don't think it's suck or sticking. My air conditioning works, fan works fine too. Really don't want to take apart the dash (but irealize i might have to)

Can anyone give me an idea of what might be wrong? Anything I might be able to try before considering a mechanic ... How much would it cost to fix approx.?