Ford dealer was around $130 for a drain and refill, when I paid to have mine done 4 years ago (yes, I do it myself now). Be persistent about getting the Mercon V, though, and not just a Mercon/Dexron swap with Lubeguard Mercon V property converter/additive. That happened to me once. Mercon V has a very distinct smell, almost burnt smelling when new, like axle/gear lube. Some quickie oil change shops will do the fluid flush for less than that, but I haven't found one yet that uses Motorcraft Mercon V, and I've had some bad experiences with a few of them for just a simple oil chage.
Don't be afraid to ask or pay for help when you recognize your limitations. It is possible to screw this up, and if you don't have any way of getting real help fast when you need it, it gets awful lonely, but if you have the facilities available and reliable help, I don't blame you for not wanting to tackle it yourself. My dad threw me into car repair 22 years ago, when I was 14, but trial and error on a VW was cheap, unlike a 4R70W, and he had years of experience to back me up.
97 LX, 4.6, Dynomax catback, Mustang MAF/intake tube and Aviator throttle body, Xcalibrator2 by Lonnie at BOC, 180 t-stat, Super Coupe wheels with 235/60/16's, Kenny Brown strut tower brace, Tokico Blues, Eibach Pro-kit, some strategically placed MN12 Performance polyurethane pieces, '02 Grand Marquis transmission
Submariners do it deeper...