This repo contains two AWS CDK applications. The first one is the v1 repo: the-big-fan from cdkpatterns and the second repo is the migrated AWS CDK v2 application.
All in all, it took roughly 30 minutes and was easy to execute. Very minimal changes were necessary. I followed the small migration guide here Announcing AWS Cloud Development Kit v2 Developer Preview
If you want to try both out its enough to change into one of the directories and run
npm install
and
cdk deploy
It might be that you first have to bootstrap your environment with the new bootstrapping process.