"Can someone give me a hint on how to install QT 3.2.3 (either by this or an alternate method)"
The problem is that the same file is included in three different packages. You can solve this problem by using the CLI rpm command.
First of all copy /usr/share/themes/Default and save it someplace safe. You may want to go back to the old copy of /usr/share/themes/Default when the dust settles.
I am going to suggest that you remove gtk+ and gtk2, install the whole works like you have already tried to do, then install gtk+ and gtk2 again. So make sure that you have the rpms for gtk+ and gtk2 handy.
Read man rpm as a reference.
Issue the commands:
rpm --nodeps -e gtk+
rpm --nodeps -e gtk2
which will remove the two packages.
Then try installing the whole kaboodle with apt-get as you were doing before.
Then reinstall gtk+ and gtk2 again with:
rpm --force -i /handyplace/gtk*
or you can use two separate rpm commands giving the full package names.
Then you possibly want to restore /usr/share/themes/Default back to its original value.
If my suggested method screws up due to unforeseen problems then you could end up with both KDE and Gnome inoperable. So you need to back up everything before you try this.
Be prepared. Create a LifeBoat CD.