Any leaks/drips under the car? Would suggest checking fluid levels before such a long trip, or having a trusted mechanic check them. The guideline is in the Owner's Manual, found here:
http://www.motorcraftservice.com/pubs/content/~WO7EDG/~MUS~LEN/40/07edgog3e.pdf
HowTo is page 299, spec & capacity of the fluid on page 304.
Basically, you need to run the vehicle for about 20 miles to get the trans to warm up fully from a cold start. Personally, I don't know if this is true since I do not have a trans temperature gauge, but that is the process I go by.
Do not check if you have run the vehicle for an excessive amount of time or at high (highway) speeds. Have to let everything get cold first (at least that's what the manual implies).
Then park, put the parking brake on, and run through the gears, giving each gear a little time to shift into it properly, and return to park. Check fluid level.
You may be a few quarts low on your trans fluid, don't be surprised. If so, you will need Mercon V spec fluid. I use Castrol, but any reputable brand should be fine.
Add a little at a time until you can confirm the fluid is back in the hatched area on the trans dipstick.
HTH.