I used to be a pro mechanic, and I'd change it IF the fluid on the stick is yellowish and/or burnt smelling. It should be red and not smell burnt.
I would change fluid and filter, never just fluid. I would clean the pan.
I would not change fluid in any auto transmission in which the fluid is still red and unburnt. I have seen many, many of these done according to manufacturer's mileage specs, and the trannies then go out or begin to leak heavily.
Basically, if your fluid is red and unburnt, and the vehicle shifts properly, all is well. I would not buy a vehicle with burnt, yellow or dirty fluid. It gets burnt by clutches slipping or overheating from severe tow use. Sometimes if you change fluid promptly enough, it will be OK; sometimes not. If you buy it, you toss that coin.