For the most part you can just upgrade. Reading the release notes and saving your configuration to a file first is always a good idea.
Gen. 1 units won't run the latest code, I think the last available is A4.11.
When you upgrade, some configuration commands will change automatically as part of the change process. For example, the keyword "ip" is added to many commands referencing IPv4 addresses because the unit is now capable of IPv6 as well. This process generally just works.
One caution is that if you ever go back to an earlier firmware, the configuration modifications made by the upgrade process won't be understood. Earlier firmware will treat the modified commands with "ip" as an error.
If you have a configuration management system such as RANCID, this won't be an issue. Otherwise save your existing configurations to a file just in case.
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