I would recommend that you ensure that you have a (working) backup before you start.

After that, you should be able to update Observium as per their update instructions. A user has also documented a script that could be used. I'd really like to use that, but when I tested it some time ago, I hit some issues. I'd like to try again sometime soon and if you test it yourself, then I'd love to hear your feedback.

Please also note that there are a few improvements that you may wish to add too. Namely fixing the MIBs setup and adding in the housekeeping cron job.

I hope that helps. Let me know how you go.

Yes; You can always upgrade that from proper initial setups.