Original Alan D'Estrehan oil painting, where to get it appraised?

I have a large original Alan D'Estrahan oil painting titled "Fisherman's Wharf" it is a highly detailed oil painting of a ship named the "Balclutha" docked at Fisherman's Wharf in San Fransisco. The painting depicts the loading and unloading of the ship at Fisherman's Wharf when the ship was in use during the 1800's. The Balclutha is still in use at Fisherman's Wharf as part of the Maritime Museum exhibit in San Fransisco. Does anyone know what this painting may be worth, or the best place to have it appraised and sold?