Installing OpenOffice 3.1 in Debian Lenny 5.0 is simple and you get all your Icons set in Gnome without the need of manually setting up links. What you need to do is:

• Using Synaptic Manager, remove your old OpenOffice (mine is 2.4) installation
• Download your .deb packages from http://www.openoffice.org/
      Start downloading OpenOffice.org 3.1.0 for Linux Debian in US English
      (Java runtime, JRE, included for all OS versions except Linux Deb and Mac)
• Unpack all those .deb that comes from your download into a folder.
• Open a terminal session into your new folder that contains the debs and type:
    dpkg -i *.deb
• Move the the subfolder called desktop-integration and retype
    dpkg -i *.deb
• Now your OpenOffice 3.1 is installed into your system. Go to Application –> Office –> OpenOffice 3.1 Base and configure you workspace

If you see this message once you run OpenOffice:

OpenOffice.org requires a Java runtime environment (JRE) to perform
this task. THe selected JRE is defective. Please select another
version or install a new JRE and select it under Tools - Options -
OpenOffice.org - Java

you should update your Java JRE: install sun-java6-jre using Synaptic Manager and your are done.