If you dont mind paying dealer labor and parts prices, there is Bryan Mitsubishi 8213 Airline Highway, Metairie 70003 .504-466-6100.
Any reputable car repair place like Pep Boys, Goodyear, Midas, Firestone or Wal Mart should be able to do this basic service for a rate cheaper than the dealership.
If your vehicle has a unibelt (a single belt that runs everything) and arent totally mechanically deficient, you can easily do it yourself. Your vehicle should have a decal under the hood showing belt routing. One belt, one prybar/breaker bar for the tensioner and a friend to assist, you could do it yourself for just the price of the belt.