I need to change out my tranny fluid. It's brown but not burnt smelling. Car doesn't slip but does seem to surge at highway speeds. I bought 5 quarts of Mercon/Dextron III. If I drain the 10mm hex bolt on the bottom of the trans will that be sufficient. I have access to a trans flush machine which I could also use if there's a good line on the car to pull off of. Should I change out trans filter too? Thanks for the help this site is great!