No, I dont change it unless it has very low miles on it or I know its history. If you have an auto trans at 100,000 mi. and its working fine, a fluid change can damage it. If you dont drain the torque converter too, you will only change about 1/2 of the fluid. If you know its been changed every 24,000mi, I would keep changing it at those intervals.
If you insist on changing it, check it now when its hot to insure that it is full. Then drain it and measure what you took out. That will be a good amount to put back in. You will prolly get around 6 qts out of it if you dont drain the converter(some of them have drain plugs and some dont). You will have to remove the dust cover and turn the engine slowly to look for one. My book doesnt say what the capacity is, it may vary. I am guessing 12-14 qts total. Try calling the auto parts store, they can usually tell you what it takes. When you fill it up, you should go slow with the last few qts and check the dipstick with the tranny hot and engine running in park. And if you change it make sure to get a new filter too. This can be a very messy job if there is no drain plug in the pan. Be prepared for fluid to go everywhere, that will make it hard to measure what you took out. I always have more fluid on hand than I think I will need.