Are you talking about a simple hardware change? I.e. with no changes to the software (Operating System, Database Version or Outsystems Platform)? Will the Domain Name or IP of the new server be the same as the previous one?
If so, the procedure should be simple. In high level, all you have to do is:
Bare in mind that if you change the Domain Name or IP of the server, you'll have to change all configurations that use those properties (Site Properties, Web references, specific application configurations, etc.).
For more details, please see the guide posted by Miguel João - Guide: Restoring an OutSystems SQL Server database backup into a another server . See also the technical note Migrating an Environment Using a Database Clone .
I agree that your idea is the easiest way to do restore the previous application data. Nevertheless, please bare in mind that when you restore the OutSystems database, you will also be restoring all system entities (eSpaces, eSpace versions, extensions, timers, permission areas, Site Properties, etc.) and application data (including Enterprise Manager users, permissions, roles, etc.).
This means that if you publish any eSpaces or extension after the backup, you must remember to download these changed eSpaces and extensions before restoring the old database (otherwise you will loose them). If this is the case, after restoring the old database you must also republish these changed eSpaces and extensions (maybe the best is simply to replish a solution with the whole environment) and redo all configurations that might have changed (Site Properties, Web References, users, permissions, etc.).