notsteve,
Welcome to Apple Discussions. Simply either pre-order a copy of the full retail iLife 09 application from the Online Apple Store or purchase when it becomes available from any place that sells Apple products. Then follow the installation/upgrade instructions. Upgrading will retain your current sites.
Except for iTunes, the other apps you mentioned are not free Upgrades. iLife 04>iLife 05>iLife 06>iLife 08>iLife 09 are all paid upgrades. There are however, free "Updates" within each of those, which is what I believe you're talking about. But those updates are usually bug fixes and minor enhancements.