I have a command-line Python script that works well to convert one sort of file into another given a few parameters and would now like to deploy this to some of my colleagues who may not know what a command line is.
I could work for hours trying to determine which Python GUI toolkit is "best", then learning how to do what I need, but it seems like this would have been done before.  
Is there a relatively cook-book method to GUIify my program?  Direction to either some sort of lesson/tutorial or an existing, documented, concise program would be excellent.
This depends mostly on your need. If your need is simple, you can just go with tkinter that is bundled with python itself. If you use this, you will not be relying on third party library to implement your GUI. Since you are wanting to make this available for your collegues, this might be easier to compile with py2exe or other similar stuffs to exe which might be tricky if you use third party library for GUI. However, if you want to add more functionality to your GUI, wxpython/pyqt/pyGTK are the GUI toolkit to look for. Personally, I favor wxpython due to its cross-platform nature but pyqt and pyGTK are also equally good as far as I have heard.
Cookbook GUI interface for a command-line script