How to Upgrade Sarge to Etch via apt
Configure Apt Sources
#Include the following: deb http://ftp.de.debian.org/debian/ stable main deb http://security.debian.org/ stable/updates main
apt-get update apt-get dist-upgrade //if anything breaks on dist-upgrade, do: apt-get -f dist-upgrade
Apt-get dist-upgrade may break if there are problems with some packages, including overwriting etc. In these cases, try to manually remove the package at fault. A dependant package may show, and it can be removed. Remove packages with:
apt-get remove package //or to remove: dpkg -r package //or to remove and purge: dpkg -P package
Thats it. Keep fingers crossed and have some time to spare. Keep note of packages you remove manually.