Just do a couple of drain/refills. I can feel a difference in smoothness after changing my ATF in the gen 3.5 and 5.5. Just remember.. If your trans fails sometime down the road, it was on its last leg anyway and it was not due to an ATF change. I swear some people find any dumb thing to blame trans failures on..like a trans flush 100K miles ago

- which is where all the rumors of transmission failure and damage come about that get blamed on changing your fluids. I can't fathom any reason why NEW fluid with all of its lubricating properties intact could be a bad thing.