Release Notes: https://github.com/DynamoDS/Dynamo/wiki/Release-Notes#310wip
Language guide: https://dynamobim.org/wp-content/links/DesignScriptGuide.pdf
Nugets: https://www.nuget.org/packages/DynamoVisualProgramming.Core/3.1.0.4724
You can also download the release version from https://dynamobuilds.com/