Originally Posted by AuSeeker

You'll get 3 different opinions on this subject...but you haven't said what year it is, I say this because the 2003 V8 doesn't have the sealed transmission and has a dipstick which to check the fluid level and where you refill/add fluid, all other years have the sealed transmission and you have to check the fluid level via a plug on the pan and refill/add fluid via the refill plug on the passenger's side of the transmission.

1. Do a complete fluid exchange, not a pressurized flush but just exchange the fluid via the transmission line at the radiator and fill using the fill plug, get the transmission to the correct temperature and then check the fluid level via the fluid level plug or the dipstick depending on model year, should take around 12 to 14 quarts of fluid, many on the forum have done this and have had no issues, just better shifting and no more "shudder" if that was a issue before the exchange.

2. Do a "Drain and fill", drain the fluid out of the pan and refill to the proper level as in the #1 option, should only be around 3+/- quarts, drive it a couple of months and repeat, then drive it another couple of months, etc., repeat this until you've done it around 5 to 6 time or the fluid looks more or less like new fluid.

3. Don't do anything other than make sure the fluid level is correct.

Option 2 and especially 3 or because of the old school recommendation of not changing fluid that has never been changed in high mileage transmissions because it will loosen sludge in the transmission and clog passageways causing the transmission to fail, this was true in the past, but fluids have come a long way since the 1970 to 1990s and don't produce the same sludge and old school fluids did.

That all being said I'm in the option #1 group, I have been doing mechanic work for over 50 years and I haven't seen the "sludge" issue causing problems when changing fluid in high mileage transmissions in vehicles made in the last 15 or more years using more modern fluid formulas, you can find how the do a complete fluid exchange in several topic on the forum that will walking you through the process, there's also topics on just doing a drain and fill.