With so many miles and no idea as to when the last trans fluid change was done ( if the PO ever did so ) the best thing to do is doing anything.

I overheard many times from mechs talking about not touching a transmission with too many miles,the main reason of this advise is because after so much miles and not servicing the transmission according to the manufacturer the old fluid builts a certain kind of junk and debries that keep the gears working properly.

On my personally experience i never touch the trans of my VX since i had no idea or records of transmission service and the few times i thought about it the mechs that i consulted always told me don't mess with it if the trans is working as it should.