Bring a pot of water to a boil and immerse the peaches in the water for 1 to 2 minutes, until the skins are loose. Remove the peaches with a slotted spoon and place them in a bowl of cold water to stop the cooking. Peel the peaches and then slice them off the pit in wedges into a bowl. Stir in the sugar, Sauternes, and Grand Marnier. Cover and refrigerate for at least 2 hours, or overnight. Serve cool but not cold.