Replacing one system of a failover pair by synchronizing the configuration from its peer instead of restoring the configuration

I got a box just faulty and an RMA is arriving today, so my best and clean approach to put the unit back to operations (to the HA pair) is by setting HA and Sync the configuration from the active node to the RMA unit.

What are the considerations I need to take ?.

So far I know is: (1) To make auto sync is disabled beforehand.

My questions are: Should I license before or after the sync ?. Is there any link you know in F5 KB to do this process ?.

Thank-you.