dhalliday
To avoid problems in sme9 with incompatible customisations, you should move all custom templates to a safe location before doing the backup
Also there are only a handful of contribs available for sme9, unoffical releases at this stage, so if you use contribs, sme9 is not really for you as yet.
In that case just upgrade using a CD to sme 8.1
To upgrade to sme 9
Backup to USB
Install sme9 on new server
Restore from backup
Use the console backup to USB for the easiest approach, you will be asked on first boot of sme9 if you want to restore from USB, then connect the USB drive
Note that CD or yum upgrades from earlier versions are not supported by the sme9 underlying CentOS version, so backup & restore is the only way.