Update ISTIO from 1.1. to 1.2 and configuration changes

A wonderful good morning (in Europe at least ,-) ) or a good day.

We run ISTIO 1.1.3 and we look forward to use ISTIO 1.2.x. Therefor I look for the right way to upgrade
our ISTIO in respekt of configuration changes.

For example, we would like to use persistant data for grafana etc. and we have now grafana configured without storage classes.
Further more did we configure grafana and so on with ingress-enabled (my fault) and we would like to use gateway and virtual services.

So, in general, may I update with other configuration and ISTIO manage the update and reconfigure
the mesh in the same way or should I consider something?

We are now in prototyp status, so it doesn’t matter if we loose historical data or s.t. like that.

Thank you in advance and have a nice day.