Hello, and I hope I'm putting this in the correct location.

I've written some code, in c#, to connect to Excel spreadsheets(basic columns of data) and build various tables from the spreadsheet data that help to show trends in the data.

I want to incorporate this logic into a web application, and I think DNN might be a good choice.  I have DNN 4.x installed and configured, so I don't really need much help there.  What I want is advice from experts/experienced DNN developers as to how you would approach this.

In the end, I'd like to have a portal where I can register users, allow them to upload spreadsheets(and be able to restrict access to uploaded spreadsheets based on role/membership), view the tables and graphs that I build with the spreadsheets by clicking a button, link, or menu item representing one of the many tables available.

So, I have a few questions:
1.  All the literature I've read so far, is all about database this and database that.  Can I work with just the uploaded .xls files directly, or do I need to pass them through a database layer?

2.  How do I set up a situation that would restrict access to uploaded files on a per-user/ -account basis and when a user logs in he/she can choose from a list of previously uploaded spreadsheets?

3.  Do I need to build a custom module to display the tables and graphs?  Basically, how do I show my tables?

Any help, general or detailed, is very much appreciated.  Thanks in advance!