>OK, I am considering throwing in the towel. I have decided to give dotnet a try. I have read several books about C# and VB#, and I believe that I will be able to write some code relatively fast. But I don't want to start in the wrong end, I want to do it right from the start, so I ask for some advice.
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>First of all, I have Visual Studio 2012 Professional installed and running on my computer. I also have MS SQL server 2012 installed and running. And I will focus on C#.
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>One of my first questions is, should I use Windows Forms or WPF Forms?

WPF is much more flexible in terms of databinding and layout.
WinForms is easier and much closer to the VFP model -but that may be a disadvantage in that you will be more liable to think in VFP terms which is probably not a good thing.
I'd vote for WPF but, as others have stated, there's a big learning curve.
Best book I've got is the Apress 'WPF in C#'.

>In VFP I have sub-classed all the base classes, some of them more than one level. Should I do the same in .net also? If so, how?

In a word 'No'. But make sure you understand the benefits Interfaces bring to the table.

>Can anyone recommend a good book (or two) with essential but not too much reading?

Not many 'slim' .net books around :-}
But best C# reference book is probably O'Reilly 'C# in a nutshell' - but it's a big nut and it is primarily a reference book :-}

Two good books to read at comes point : 'More Effective C#' and 'Effective C#' by Bill Wagner.
A subscription to PluralSight is probably a no-brainer to get you started.

>Are there other important decisions I will have to make early in my learning phase?

For a data layer you should probably go with Entity Framework or nHibernate rather than raw ADO.NET.
Again more of a learning curve but you'll be dealing with data as objects rather than tables and columns.

I don't know what type of apps you develop but Rick's suggestion of a web-based option with Angular and WebApi might be worth considering.

>And last, please don't mock me! I will always remain a VFP lover, and I know that I haven't always written nice things about dotnet. From now on I will avoid writing negative about dotnet until I know better what I am talking about.

Welcome to the fold :-}
By coincidence, I'm going to have to re-learn VFP - got to add a big chunk of functionality to a VFP app that's 15 years old and hasn't had a change in the last 8.