http://www.subsim.com/radioroom/showthread.php?t=166320
There is the link to the thread about MaGui. makman94 (the author of MaGui) has a link to his filefront page in his signature. You can download it there.
Also, the post has some nice screenshots of the GUI. But, you will definitely want to read the documentation that comes with MaGui; there are a lot of tools in there, and they take some getting used to.