As I said there was no announcement made of 2.51 there is a download yes. However that download should be the same as 2.5 only a fixed plugin as I pointed you to already.
There is no upgrade script to run just reimport the actual product so you can get the updated plugin which you even commented on in this thread. Potential SQL Injection
I am really confused here because you say in that thread everything is taken care of there.
What is it your really asking?
If you have downloaded 2.51 already you simply run the install script select the option to reimport the plugin that will update your code with the new plugin or you may manually insert the plugin contents by downloading the plugin there and update that one plugin.
That is the only change to vbgallery 2.5 to 2.51