I am not sure what a skybox is, but I think I can give you some advice in the choice of language and environment.

An object oriented language:
I strongly advice you to choose an object oriented language. Or in other words: I wouldn't try it in Visual Basic 6. I would go for one of the following: VB.NET, C#.NET, C++.

OpenGl and DirectX:
If you have some experience in the field of programming, then try either OpenGL or DirectX. I guess you have heard about these 2 . Both are capable of rendering 3D objects, textures, light, materials, ...

There's a lot of documentation on how to do it in OpenGL in C++ and there are very good tutorials available. It is also possible to do OpenGL in .NET. For this you can either use the Tao Framework or SharpGL, or other OpenGL wrappers.

If you prefer DirectX it is also adviced to do it in C++. If you want to do it in .NET there is something called "Managed DirectX".

What's better?
If you want it to be crossplatform then you should choose for OpenGL. If you don't mind about it being crossplatform, then still OpenGL is a good choise but also DirectX is possible. Keep in mind though that Managed DirectX is pretty slow while OpenGL in .NET is almost as fast as OpenGL in C++.

An advantage of DirectX is that it supports the loading of .X files (3D models). But OpenGL has no standard filetype support. In OpenGL you will have to write that yourself if you want to save/load your "landscapes" or whatever.

Moving around in a world
That isn't so hard. If you choose for OpenGL you could use the following glu-function:
Code:
gluLookAt(position_x, position_y, position_z, lookat_x, lookat_y, lookat_z, up_x, up_y, up_z);
This tells the position of the camera, the point it looks at, and defines a vector that shows which side of the camera points up.

In DirectX there certainly is something simular.

3D Engines
There are also some finished 3D Engines available that you could use. If you are not that experienced in the field of programming that might be useful. I am not sure if it is that much easier though. I tried it once and it turned out it was harder than doing it directly in OpenGL.