It is very easy to upgrade from 4.8-5.31. The documentation folder has the upgrade instructions.
Basically you would upload all the files except config-inc.php and run upgrade.php. ONLY RUN EACH STEP ONCE. When done your fine. If you where seeing duplicate errors and the like it means you where running things multiple times and this is why when you where done no images showed.
http://www.z28.com/gallery/