As far as the upgrade goes, is this document not sufficient?
http://www.solarwinds.com/documentation/LEM/Docs/SolarWinds-LEM-UpgradeGuide.pdf
As for a roll-back, I'd think the easiest plan would be to snap-shot the appliance before the upgrade, and roll-back to that in the event of an issue. Otherwise, you're looking at needing to backup the database and configs, upgrade, and redeploy and restore in the event of an issue.
SolarWinds Knowledge Base :: Configuring Backups on LEM Appliance for versions 5.6 and later