92 Ciera Tranny Q's

1992 Olds Cutlass Ciera SL w/V6 3.3/3-spd OD
146,330 miles

I have records for this car dating as far back as 1995, and I see nothing about the tranny fluid being changed. Fluid smells strange, and is dark in color. Tranmission still shifts perfect though, aside from a hard clunk from reverse to drive or park to reverse or drive when cold. Would it be a bad idea to change the fluid and filter at this stage? I don't want to do a flush as I've heard horrible things about them. Any opinions would be appreciated.

Thanks in advance,
Rich!

*bump*