Happy to help.
Generally, unless there are compelling reasons for keeping the old logs and if you are running log servers and SmartEvent on VMs, my recommendation is to simply shut them down, rebuild anew, re-establish SIC and start using those.
That being said, 80.30 to 80.40 i a minor version upgrade and you should be able to perform CPUSE upgrade in place.
Download the 80.40 using CPUSE "Recommended packages" on VM, run the upgrade verifier.
If it does not complain, you have an option of in-place upgrade.
If you have some customization that worth keeping (log exporters, custom reporting and notifications, etc..), try the upgrade.
You can snapshot the VM beforehand to fallback if necessary.
Just remember that once upgraded, you'll have to change the version in the Log Server object and install database (from Global Properties). Same goes for the fallback.
If your VMs reside on NFS, do not keep the snapshot for long: the performance will deteriorate.
One more thing: If you do decide to go with the fresh VM, do Gaia "save configuration" <filename> on the old VM and download it using WinSCP.
Shut it down and build a new one, replicating FTW steps to get the same result as the old one.
Once the new one is deployed with the same IP and the hostname, transfer the saved Gaia config to it using WinSCP. Load the saved Gaia config using this procedure:
In clish:
set clienv on-failure continue
load configuration <filename>
set clienv on-failure stop
save config
to get the OS-specific settings transferred.
Change version in the object properties
SIC
Database Install
Policy install
Once again, This does not preserve logs, custom reports, forwarders, etc...