I believe that export/import is only for content classes and not the objects themeselves.
For each version of ezPublish, there are scripts located in
./update/common (for scripts and the like) ./update/database (for db structure and the like)
If all your ini file modifications are done in overrides you should just be able to place the new version over the old version (take a backup first!!!) and then update the database with the appropriate scripts (also take a backup first!!!)
3.3 only supports import/export of content classes, while the new 3.4 supports import/export of content objects as well ( including binary files, images, etc. )