Ubuntu has a great community. As for the upgrade you should be able to upgrade online from 7* to 9* but will require to do multiple upgrades. It is easier to backup, download the the latest and reinstall.

For the future if you do the install and create a separate /home on another partition, future upgrades won't affect your home directory so you won't have to copy over your backed up data every install.

Plus if you use a separate /home partition you can switch distros from ubuntu to suse to gentoo to whatever and not worry about your data (as long as you don't format /home )