I looked into this. The torque converter does not have a drain, so you can't easily get the fluid out. The only options involve opening up the ATF cooler lines and swapping out the fluid while the car is running (many shops have a system that will push fresh fluid back in while it takes out the old fluid via the cooler lines), but I've hear of lots of bad results from those things, so, I don't think there is an easy way to get all of the fluid out in one shot.

However, doing the second fluid change, just drain and fill only, was very easy and took less than 30 minutes.