Sorry, forgot to talk about the tranny fluid, unless your due for a tranny fluid change, I don't think I would spend the money to do it. I think the recommended Ford interval is every 30,000 miles, but if you have overheated it at any point i.e. anything over 225 degrees than the fluid is no good and I would change it. I always use the Mercon stuff from Ford, but I'm sure others will chime in and recommend something that's thought to be better.
Once you get the cooler in you'll need to drive the truck, warm up to normal tranny temp so it's circulating through the new cooler and check the tranny oil level. I've been told you'll probably need to add 2-3 qts of fluid because of the larger cooler capacity.