How to implement Image Gallery custom module in a node.tpl.php.

I am a beginner. So my questions can be wrong. I know how to create a module or theme in simple way. Now I have a image gallery with pager. I have some text as well.
I want to create a page with text and image gallery. I can guess, I have to create a custom theme and the custom theme should have node.tpl.php file , which should be containing image gallery, which is a module.

Please please, somebody tell me how to integrate a module with a node.tpl.php of a custom theme. Theoretically how it should work?

Hope I could explain my question. If you find I have conceptual problem , then please also help me to understand how theme and module for image gallery should work.

Best regards.
Rajia