The transmission has never been flush or had new.

Most manufacturers recommend having the filter and fluid replaced every 36,000 miles. I too let that go on one of my vehicles. It's an '88 Grand Caravan that I use to drag around a tandem axle enclosed trailer that's bigger than the van. The filter was replaced once, at 84,000 miles because the $3.50 side cover rusted out and I was in there anyway. Now it has 240,000 miles. That's not neglect, ... That's abuse. I don't recommend you do the same thing. I'm not convinced a flush is needed on your car. In fact, there have been a few anecdotal stories about high-mileage transmissions developing problems after being flushed. I don't believe all the reasoning or stories I've heard, but to be safe, I'd stick with a simple fluid and filter replacement. That will replace three to four quarts of the fluid which is about half of it.