Harmonic Balancer on 2004 Subaru Legacy

Good Day

My alternator belt snapped I replaced the belt and it keeps slipping off whenI went to parts store to buy a/c belt since ithad also needed replacement. Parts manager came out to lookat car and stated I needed to replace harmonic balancer and that the alternator belt was staying on by tension. Could you give me an estimate on how long it would take in labor and the average cost of repair?

Asked by for the 2004 Subaru Legacy
I believe the pulley from Subaru is about $150, list the pulley for about $72, I am sure Napa have it as well. The labor to replace the pulley and readjust the two fan belts is about one hour to 1.5 hour. Cooling fans and or radiator needs to be removed to get access to the crank pulley bolt.