Some would have a "Firefox3" option in their respective repository or package manager which makes the update very very easy (APT/YUM/RPM). These allow you to c

Some would have a "Firefox3" option in their respective repository or package manager which makes the update very very easy (APT/YUM/RPM). These allow you to check the box and press "update". PCLinuxOS does this, for this specific upgrade, if I remember correctly (Firefox2 -> 3). Others that require a little more work let you just download the tar.bz2 file, decompress via command-line it in the appropriate directory. But sometimes it takes a bit of reading the documentation to understand how to get the symbolic links and such launching the correct instance of the browser. Actually, I don't know if I should be attempting to answer your question when I'm so tired. Hope that makes sense.