Combine first 3 ingredients in a saucepan. Stir in milk; let sand 1 minute. Place over low heat; cook 5 minutes or until gelatin dissolves, stirring constantly. Remove from heat; stir in syrup. Let cool. Position knife blade in food processor bowl; add peaches. Process until smooth, scraping sides of processor bowl occasionally. Combine peach puree, gelatin mixture, yogurt, and vanilla in a large bowl; stir well. cover and chill 8 hours. Pour mixture into a freezer can of a 1-qt hand-turned or 1/2-gallon electric freezer. Freeze according to manufacturer's instructions. Allow to ripen 1 hour in freezer can.