Upgrading Caudium is simple. You should install it as if for the first time. That is, get the new sources, unpack them, run ./configure; make; make install and that's all. The new Caudium installation will detect your old Caudium and keep all your old installation including your config files. The config files will be compatible with the new version so you will never have to begin the configuration task a second time. The old server directory will be saved as server.old and so the new one will be put in the classical server directory.
If you use a package system, just use the upgrading features of your packaging system.