Is it too ambitious or not to have "a good foothold" in those technologies? That's entirely up to you. I can say I have such a foothold, and I think I am pretty average when it comes to developers in general. So why not?
As to what to start with, it would depend upon what technology you were best at previously. I myself started .NET by starting with VB.NET (I was mainly a VB5/6 programmer) and found that I liked C# far better. Try both and see which catches your fancy. There are sometimes religious wars over which is better, but these are far from won by either side.
My first attempts were with Windows Forms. And I think that was a good idea because it helped me get into the framework at lower cost. When you deal with ASP.NET web apps, you have to get into an extra layer. But YMMV. My boss started with ASP.NET web apps from just about the same launchpad as me, and he did just fine (except that he is deathly afraid of winforms lol!).
Finally, I think you should start off with a good tutorial book like C# For Dummies, or . If you prefer, VB.NET for Dummies. Just work your way through one until you start feeling comfortable, then maybe start building something of your own.
For tools, you can download Visual Studio 2010 Express for free from Microsoft.
One thing you might also want to consider, since it will probably become "all the rage", would be to get immediately into Windows Phone 7 programming. There are all kinds of free tools, tutorials and other information coming out on this now, and WP7 programing will involve you in both C# AND Silverlight programming, and XNA game programming if you are interested in that. See Paul Thurrott's Windows Phone Secrets blog for information on all of that.
Most of all, Have Fun! .NET Framework programming is the cat's pajamas!