No heat

[scotts96gt]

A friend of mine put her car into a swamp several months ago. I know awesome right? Well after it all dried out the car still runs just fine except she can not get any heat. Air conditioning vent and fan all work but it wont switch to heat when the dial is turned. To me this sounds like a vac leak somewhere in the dash but the shop said their is a computer behind the glove box that probably got wet and went bad which would require the entire dash being torn apart to get to and replace. Is this a possibility? Suggestions?