Transmission fluid change or flush or both (1997 Ford Taurus GL)?

I just got a 1997 Ford Taurus GL with over 133000 miles. The car is in pretty good shape but when I shift gears it shifts kind of hard. I have no idea if the trans has ever been serviced but my guess is that it need to be. Would you recommend just draining the pan, changing the filter and gasket and replenishing the fluid or should I do a flush? Not a power flush. Just using an extension hose to drain the old fluid and add new fluid. Or do you recommend both? If so, in what order?

Transmission fluid and filter changes are required for all the AXOD transmissions used over the years. Flushes are risky and can cause failures of otherwise good transmissions.