2000 Mitsubishi Diamante Vacuum line?

I have a 2000 Mitsubishi Diamante with roughly 110,000 miles. The vents in the car only blow on the sides. The floor, front, or front defrost vents dont blow any air; hot, cold or a/c. I have been told that this is the cause of a broken or damaged vacuum line. My next question is if this is a vacuum line is it something easy to repair and were would I find that vacuum line? thanks in advance!