newbie Advice for app design

[tgate]

Beginner question...

My apologies if this is not the correct forum for such a question.   
Please let me know if that's the case.  I'm getting my feet wet with  
GNUstep and cocoa and this list has been really helpful.

I've currently been experimenting with various components of what I'm  
trying to do and now I'm looking for the best technique for tying  
everything together.

What I'm trying to do:
	- Build an app which can view an Image, Image sequence, Movie, and/ 
or 3D geometry file.
	- if multiple files are loaded I want to wipe between them within my  
NSOpenGLView.
	- I would also like to be able to open other windows to view one or  
more files.

My Question:
	- Should this be constructed as a "Document-Based Application" or  
simply an "Application".

My Confusion:
	- If it is a document based application how do I deal with loading  
multiple files into one window?
	- if it is a standard application how do I deal with opening another  
copy of my main window?
	- in my mind it is similar to the way Xcode (or those familiar with  
textMate) is designed.  Multiple documents listed on the side which  
when selected are loaded into the main portion of the window.

Or is this really a mute point?  When I design my NIB file I'm not  
sure if I should design something different for a MyDocument.nib or  
simply build one Main.nib which can load different documents.