How to backup Ubuntu - for Upgrade Ubuntu 8.04.1 to Ubuntu 10.4LTS potential issues

Currently in place - Ubuntu 8.04.1, as a File Server (Samba)/Web/Mail
Looking to upgrade to Ubuntu 10.4LTS

I have given a cursory look at
http://data-recovery-software-articles.blogspot.com/2010/05/how-to-upgrade-from-ubuntu-910-or-804.html

I have no Ubuntu experience, less installing it on a desktop.  
I have good knowledge of Microsoft Updates
I want to have a rock solid backup of 8.04.1 incase something goes wrong.
What is the process for backup and restore.
RAID1
How can I verify that the backup is a good one?