What is the best way to change the ATF fluid on a 2003 X type
The best way to replace the Automatic Transmission Fluid fluid (ATF means Automatic Transmission Fluid so no need to add the word fluid, (redundant)) is to remove the drain plug on the bottom of the gearbox, replace the plug and fill the gearbox from the top through the fill port.
There is a ‘standing-tube’ in the bottom of the gearbox that will ‘dribble’ fluid when the level is reached at 30 to 50 degrees Centigrade (engine running in Neural or Park). You install the level plug and shut the engine off.
Same procedure as a VW with the 09A gearbox because it is the same gearbox. (JATCO JF506E)
Internet search will likely yield many YouTube videos.
Thanks , try it this weekend