Hi David,
If you need to compile the module (if it has a DLL) then you cannot just copy the page and module and make changes to it as the source code will not be available.
However if you use the module creator and the script/razor approach - you can potentially do that. http://www.dnnhero.com/Videos/DNN-and-the-Razor-Syntax
There are many ways to skin the cat (to create modules on DNN)
Best regards,
Aderson