Simon,

First, here are some good web sites with information.

http://www.syncfusion.com/FAQ/WinForms

This is an EXCELLENT web site for Winforms. There is a ton of sample code on this site. This site is worth more than 10 winform books combined.

http://www.codeproject.com (another great one)
http://www.windowsforms.net
http://www.gotdotnet.com/
http://www.dotnetwire.com/
http://www.datagridcolumnstyles.net/easyDataGrid.asp
http://www.businessobjects.com/products/dev_zone/net/how_to.asp
http://www.wintellect.com/
http://www.csharphelp.com
http://www.mastercsharp.com/
http://www.learnvisualstudio.net/


Second, of all the .NET books, here are (IMHO) the must-haves...

1) C# Essentials by O'Reilly Press...a cheap ($25) but awesome reference
2) .NET for Visual FoxPro Developers by Kevin McNeish and Cathi Gero
3) Essential ADO.NET by Bob Beauchemin
4) Crystal Reports .NET Programming, by Brian Bischof

Also, Jessie Liberty has written some very good .NET books for O'Reilly Press

Third, the .NET forum here on the UT probably has the equivalent of dozens of books on it. Just do a search on MDI Parent, or interfaces, subclassing, etc...and you'll see a large number of questions and posted solutions.

As for your last question...what you described is essentially what I have...an MDIPARENT form, where every form (customer form, order form, reports form, etc) is a child of the MDI parent.

Good luck!
Kevin