Thanks for the tips!
I got both vncserver on the server and VNCThing on my PBook up and and running and even the ssh tunneling working.
X Windows seems to work ok (tested with emacs and gimp), but when I run runInstaller from the console, the process just says:
[oracle@swissnet Disk1]$ Initializing Java Virtual Machine from ../stage/Components/oracle.swd.jre/1.1.8/1/DataFiles/Expanded/linux/bin/jre. Please wait...
After 20 minutes I'm getting a bit tired of waiting...