Flushing Is Best Option....If Car Is All Fine...There's No Need Of Messing With Filters....!
I Mostly Don't Trust People Out There Who Knows Least About These Boxes....As A Result...They Can Mess It Up For Nothing...And You Have To Pay Price...!
So As Rule Of THUMB Says...If It Don't Need A Change...Don't Mess With It....ATF Change Alone Will Be Enough....!
If You Feel Its Conteminated ..Flush It With Some ATF Till It Comes Out Clear....!