[Zope] Upgrading from 2.3.3 ---> 2.4.2 on Linux

I looked through a lot of the docs and changes but cannot find anything specific. I have a very big 2.3.3 installation (with an entire copy to play with) but I am not sure the easiest way to go about the upgrade. - I can install 2.4.2 just fine (it compiles and runs) Should I build a clean 2.4.2 and move over all the stuff (a pain)? Unpack 2.4.2 into the 2.3.3 directory and just build it over the old one? What I would really like is the 2.3.3 --> 2.4.2 update file which seems not to exist? Anyone have some hints before I spend more time banging my head against a wall? BZ