Microsoft has produced an automated set of scripts that will do this migration for you; you can find them here. This process will do the work for you, but there will be some downtime as the migration occurs. The downtime should only be a few minutes, but please bear in mind this section of the doc:
The upgrade normally takes a few minutes for the script to finish. The following factors may lead to longer upgrade times:> - Complexity of your load balancer configuration> - Number of backend pool members> - Instance count of associated Virtual Machine Scale Sets or Virtual Machines> - Service Fabric Cluster: Upgrades for Service Fabric Clusters take around an hour in testing