Wyse Device Upgrade from 4.9 to 5.7

We are currently on WDM 4.9 version and would like to upgrade it to 5.7.1 or to the latest available.

Below is the infra.

1. We have a single server , configured for ~4000 devices.
2. Database Rapport is local to the server.

What would be the upgrade process with low risk and impact and what precautions should be considered for an upgrade.

I am planning to have a clone of existing server and perform an upgrade there, test it and then move to original server, But could not find any documentation on the website.

Please suggest

Thanks

Datta