you can surely import it however I am not sure about the ability to change the imported model,make sure you change everything you want before importing it or import it and if you see that any change is needed,start over the process!!I am waiting other people's comment,this is an interesting question
We can change the parameter of model from CST itself, after design model in CST by using symbol for each dimension, you can go to parameters list and change the dimension and ask to ensure press F7, as Rbert speak.
As, you can used sweep parameters in CST to studies the change of one parameter.