This is a long lingering question as to change or not. I can't say one is better than the other because I used both methods in the past. On my LS400, I went to the Toyota dealership and bought a case of Toyota tranny oil. Seems it comes rather amber if I remember correctly, not red like Dextron.
I drained (there is a drain plug on the transmission pan), measured, refilled, drove, drained, refilled, drove and such until the case was gone. Did it right in my driveway. Probably not the official method but I do know the car now has in excess of 200,000 miles and the transmission is still perfect. Oh yeah, did I mention how much fun it was?