Auto trannies are a mystical, magical thing.. if you find a good tranny guy, try not to upset him
. My tranny guy has been building trannies since he was a teenager. I told him I'll tell everyone what a good job he did on my car, his remark "I will only work on YOUR car". He will not work on any performance aod mustang except mine, too much of a headache.
He explained to me once that residue builds up in a tranny if it isn't maintained regularly. If you change the fluid later then it loosens the residue and build up and clogs causing the tranny to burn up(due to the heat I assume). So I would say changing the fluid would be worse than not at this point. Good luck with it..