Changing CULL Mode

[Halsafar]

Showing my ability to apply the knowledge I have learned while D3D'in I figured out how to fix my skysphere.

The sphere generation code was well written by someone. It was for OpenGL tho. It was also created to create a dome which is to be see from the outside.
Well I needed a Dome that can be seen from the inside. So after re-arranging the vertex allocation, or trying to create a dome with a negetive radius I saw each had some graphical problems....Neither worked for me.

SO

I decided to change the CULL mode to None, then render the skysphere, then change it back to CCW.

Works like a charm.

So my questions are:

D3DCULL_CCW -- remove counter clock wise triangles?
D3DCULL_CW -- remove clockwise triangles?
D3DCULL_NONE - Remove nothing
D3DCULL_FORCE_DWORD -- What the f___???

Does changing the cull mode cause any lag? doing it each frame?
Is there a better way?

What changing CULL modes should I save the old mode, or not?
Will it matter?
Can it be different than any of the 4 modes above????