> Module @ #(VMConstruction) 
> 
> This gives just back the UndefinedObject.
> 
> 
> What is happening here? Actually I would like to unload the VMConstruction
> module the one I think I've read should be unloadable.

Try : Module @ #(Squeak VMConstruction)
You will get the result expected.
Also you can try moduleTool : 
	http://www.iam.unibe.ch/~bergel/Smalltalk/moduleTool.html


Regards,
Alexandre