It will be fine....
Make sure the Ex has at least 3.55 rear axle ratio and a transmission cooler.
I towed a 2000 31 ft TT with an Expedition 5.4 AWD with 3.31 and it towed significantly worse than the 3.55 of my 97 F150. For my trailer it was the difference between living in 2nd gear all the time and spending less time in 2nd and more time in 3rd.
I'm actually looking of a 97-01 Expedition as a possible replacement to my 2000 town car so I can get another TT.
Just watch your axle ratings and use WD with sway control.
Thanks!
Jeremiah