Take out the glovebox and take a peek yourself first. Maybe it could be a simple ducting problem or electrical problem. Also check your heater if it is working properly (when the engine is hot, of course). Check if all the vents blow the same temp of air.

Pulling down the dashboard (esp. with airbags) is a task that requires skill to do correctly. Sure anyone can take it out. It's putting it back together that worries me.