Trans fluid change must be dealer ? or Valvoline Hi mile sp3 okay ?

Hello, The cost on that is going to be high because of the fluid. Most shops can flush it to avoid the cost of buying fluid twice, but you still may be able to do it cheaper at home. Any SP III certified transmission fluid is fine. If the Valvoline is branded SP III, you should be ok. In the owners manual there should be (emphasis on should be) a section detailing the certifications for the transmission fluid that you need. Check it out to make sure there are no other requirements listed.