This is a common practice. I've done it countless times on various makes and models. Some cars, like Honda, don't even have a pan. But on the Ford, order an aftermarket Mag Hytec pan & filter. Increased capacity, cooling fins, built in gasket, and a magnetic drain plug. Some cars are better off with OEM spec fluid (Honda ATF-Z1), and some are better off with aftermarket synthetics. In my Fords, I've successfully ran Lucas Oil, Red Line, and Royal Purple. Ford has issued a TSB that all prior models that were spec'ed for Mercon should use Mercon V. At my local Ford dealership, Mercon V is $4 a quart, compared to $15+ for brand name synthetics. Try to avoid Wally World's multi-grade ATF. Your vehicle should have a transmission fluid capacity of 14.5 quarts (17.5 w/ Mag Hytec upgrade). It is a good idea to have 2 cases of fluid on hand. I have seen up to 20 quarts used before clean fluid came out.
Drop pan, remove filter, then replace with Mag Hytec upgrade.
Fill from dipstick tube with new capacity (up to 8 quarts) of ATF.
Disconnect line to cooler and run into a 5 gallon bucket.
Turn on engine.
Pour ATF into dipstick tube until fluid coming out to bucket is clear.
Turn off engine.
Reconnect transmission cooler line.
Turn on engine.
With vehicle in "PARK", check dipstick, top off to fill line if necessary.
On my vehicles, I perform this procedure to replace the OEM fill with Royal Purple at 10,000 miles. Then I drain the pan & clean the magnetic drain plug every 10,000 miles. Overkill? Perhaps. But there's no such thing as being only a little pregnant. You can decide on your own intervals to suit your driving habits.