I have a Ford but it's not a Galaxy (yet) at my local (well not that close) and this is what they did - drop pan, empty old A.T.F. then replace for new filter, seals, pan gasket and sump back on. Using the 'T-Tech' machine via Radiator cooling pipes to remove the remaining old A.T.F. from the Torque Converter then pump the new fresh (my choice of) A.T.F. in. This is done at every 30,000 miles (including adjusted the Brake Bands) to keep the Auto-Box in shipshape without any over heating breakdowns or any Auto-Box issues. I have found this kind of method gives no lost of performance or Fuel economy. P.S. A dirty M.A.F. (Mass AirFlow Sensor) can cause gearbox malfunctions, incorrect ratio errors, loss of 4th gear or torque converter clutch (T.C.C.) operation. The M.A.F. should be cleaned or replaced before having the gearsbox overhauled at great expense. Hope this helps!