Lots of us tow campers. Mine is 23 feet and should be under 6000 pounds but the aerodynamics of a brick drop fuel economy significantly when towing. No problems with the "short" wheelbase on my '17.
Trailer brakes are usually mandatory by state law once a trailer hits 2000 pounds and the late Expeditions have very capable brake controllers built into the vehicle.
Over 600 pounds on the ball requires a weight distribution hitch (WDH). I've used the Equalizer (brand) for a decade and highly recommend it over the chain and sliding sway bar arrangement of the cheap devices.
If you have the air suspension keep in mind it has to be Off to set up for a trailer. Same warning for any gimmicks like helper springs and "timbrens" (sic?) which also disguise overloading.
As for what trailer to select I have two "rules" (which I, frankly, made up!) The
1000 Pound Rule states the trailer has to weigh 1000 pounds less than the towing capacity. In this case it is limited to about 8000 pounds. That rule works but is pushing the limit. I'm more happy and use the
One Ton Rule which limits the trailer to 2000 pounds less than max capacity to account for those hot summer temperatures, high altitudes, and long grades. This means no more than a 7000 pound trailer. Either of these "rules" are conservative and avoid more than 4th grade math. Somewhere in the middle maybe?
Owning an Expedition strictly for towing a few times a year -- like me -- makes no sense financially. But there it is!
-- Chuck