Tagging myself onto this to follow.
We have a 2011 Expedition EL that we also added the tow package items to.
FWIW we pulled a Keystone Cougar 29BHS for several years. Never had any trouble, but they were fairly tame trips. Dry weight I think was 6300 or so with tongue weight of 870.
Recently upgraded to a Coachmen Apex 300BHS. Overall it's a couple hundred pounds lighter and significantly so off the hitch. Towing back from the dealer it seemed to be a smoother, more controlled ride. The manufacturer numbers put dry weight right around 6,000 with hitch weight around 670.
I did a ton of searching when we first got the Expedition. Finally ended up with adding the wirings, a brake controller and a really large transmission cooler. Found out that it came stock with the larger radiator. Other than that I couldn't figure out what the "tow package" included.
