In addition to what kjd suggested, it will be easier to treat Sammie as the number one dog.
Make sure Sammie will have your attention, foods, treats, walks, anything first and Sparkie will be the second. It has nothing to do with the size or which dog is more dominant. YOU can decide the pecking order, not between them.
By doing this, Sparkie will treat Sammie with respect and Sammie won't have to be threatened by the new addition.
Good luck
