My mechanic keeps telling me to not change the fluid, unless it's really harsh use.Agreed. The only tranny I have ever had crap out was the only one that I changed the fluid and filter in.
New, slipperier fluid can make problems worse.
The only Chrysler mini-van I recall changing the fluid on (a 1990 Grand Voyager), they found pieces of snap ring in the bottom, but the transmission had no issues other than some jerking for a few minutes A YEAR BEFORE.
(I can't say for sure that I never changed the trans fluid on any other vehicle.)