Help with texture applying/copying and setting values script

I need a script that does the following:

1) apply one texture from the library in the Diffuse Overlay Weight channel (I don't know if it's called "channel" or not, but I guess everyone can understand it; in case it's not, pardon my ignorance);

2) set the value of the overlay weight;

3) copy the texture from the Base Color channel (a.k.a., "diffuse") to the Diffuse Overlay Color channel;

4) set the value of the diffuse overlay color.

All this with a character selected so I don't have to manually input anything into the script (i.e., type it). Does anyone know how to do this and can help me?

EDIT: and I also need to set a new limit to the Diffuse Overlay Color channel.