I think what you will see now is many Top Republicans getting behind Trump before he seals the deal himself. You don't want to be the last guy on the band wagon very little favor accrues. Trump will accept most of them in the name of unifying the party.
I do agree that Trump will probably ask for changes in the RNC once this process starts and rightly so. The RNC is damaged goods right now and will need a change to effect a strong campaign against the Democrats. Preibus will probably have to step down before the campaign starts in earnest. He is not the face of the Republican Party you want to go up against the Democrats.
Yup. Priebus is another unethical empty suit,much like Cruz. Both are loathsome individuals.