How do I service my transmission???

[cxt2001]

Ok heres the deal...The dude before me put a new tranny in at the dealer around the 85K miles mark and the car now has 140K miles on it. And basically I was wondering how to service it because I hear a flush can be detramental to the tranny, and a drain and fill just doesnt do much good...So what can I do??
And by the way it is acting alright except for sorta hard shifts sometimes, but no slippin' yet... Any help is great.

Thanks