tripower,

In many cases you can simply use the module as a wrapper around existing functionality. However, you may wish to customize your logic to start leveraging some of the DotNetNuke frameworks' resources.

Although it doesn't talk about taking your existing code and turning it into a DotNetNuke module, check out http://www.adefwebserver.com/DotNetNukeHELP/ for some tutorials on creating modules. I'm not aware of any tutorials currently that talk through the process of converting/wrapping code, probably due to the fact that it would be hard to know what to tell someone to do without knowing the ins and outs of their specific code....

Take care,

Ian