Hi,
First and foremost: before attempting this, make sure your applications can actually work with quorum queues.
There are subtle differences in some behaviours and there's a feature not supported by quorum queues currently (priority queues).
If your applications declare queues, just importing modified definitions won't work, because what the application will try to declare won't match the existing definition. There's a currently somewhat hidden feature to avoid that - when declaring a vhost, you can specify the default queue type. This way if an application tries to declare a queue without specifying the type, it may get a quorum queue instead of a classic queue. Check --default-queue-type in `rabbitmqctl add_vhost` and
https://github.com/rabbitmq/rabbitmq-server/pull/5305.
Best,