The SQL Monitor repository is no different to any other SQL Server database. As such, any method for database replication will probably do (mirroring, replication, log shipping).
Our SQL Backup product allows you to set up log shipping with ease, so if they have a licence you have a quick win.
The data purging will mean that replicated or mirror DBs lose data over time. If this is unacceptable, then I'd just recommend taking full backups and restoring them when you want to analyse the time period that backup relates to.
As for the actual analysis, you can install SQL Monitor locally and point it at the restored database. To prevent it from modifying your copy, it is essential that you configure your local copy of SQL Monitor to be in 'slave mode' (=read only). Details of this I can email you, if that's what you want to do: email@example.com