Hi. I agree with all the others -- flush the wrong stuff out.
And let me tell you, it was so easy. I had posted some questions about using IPDs kit a day or so ago. Well, I did it earlier today and let me tell you, I could have done it wearing a white shirt and suit. It was SO easy and clean. I ran 12 quarts of fluid through and I've got the freshest looking ATF on the planet right now.
All I needed was a 15mm flarenut wrench, a funnel that can reliably stay (viz. a narrow neck) inserted in my tranny dipstick tube, IPD's special hose, and three 1-gallon "bottled water" jugs.
I unhooked the upper connection to the radiator, hooked up the hose to the radiator output, ran the hose into the jugs. Had my wife start and run the engine while I stood by the jugs and watched their levels. Had my wife turn off the engine halfway up, put in 2 qts of new fluid, restarted, stopped at a full 1-gallon, refilled with 2 qts, changed jugs, and repeated three times. That's 3 gallons of fluid or 12 quarts exchanged. Spilled maybe one drop when I unhooked the hose -- that's the total "mess".
Do it!