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I am just now working to install- set up the gallery,:scared: I dont understand all this code at all. There is step by step instructions but it is still daunting. I guess I better save a full backup of the site befor I start, so I can reload if I mess it up. And yes I am using a rental "my domain.com"

I don't know what kind of gallery you are installed. But if it is Gallery 2, you may check Gallery 2 Codex Page for integration.

I'm sorry, I don't know about phpBB3. Once I've setup phpBB1 for my friend, but mod (extension) install/uninstall is very difficult, especially for Japanese translation. So when I start my forum I chaged to SMF and Coppermine Gallery, because more easy mod install/uninstall and integration. 

Basically, for integration (or bridge) with forum and gallery software, you don't understand the code but you should know your forum and galley's installed directory structure exactly, and use same database.