Go for it -- it's the simplest do-it-yourself job you can do for so much benefit (someone said, "most bang for the buck")!
But remember -- when you try to loosen that top ATF line's fitting on the radiator, be SURE to use a "flare-nut" style wrench, not an ordinary crescent wrench. The Flare-nut wrench has more corners, or lands, than an ordinary wrench -- it looks like a closed or box wrench with a portion cut out. Thus, it grips the nut better, with less likelihood of slipping and rounding the corners. And I think the size is 15mm, but I'm not sure -- maybe someone else can recall it more specifically.
Also, be sure to only change about 2 quarts at at time. That is, run the engine until the fluid, filling a clear gallon plastic water bottle is about half-way up, and stop the engine and then add 2 quarts of fresh fluid into the dipstick tube. Repeat by restarting the engine, until the fluid now fills the gallon container, and then shut it down and add another 2 quarts. Repeat until you've gone through about 12 quarts.