If there is any possibility you will tow with your Navigator, you should absolutely get the tow package. One feature not mentioned yet is sway control.
This does not eliminate trailer sway, but can be an early warning of a very dangerous situation, giving you the opportunity to correct the situation before
disaster. In addition to the items mentioned above, without the package, you may find you will have to acquire several items that are included. This might be
one or more fuses to activate circuits needed for proper towing.
I started a thread a few months ago to get input on weight distribution hitches, something the manual requires for trailers over 6000 lbs. Since my previous vehicles
didn't need it, I had no experience with this type of hitch. I can assure you if your tongue weight nears 600lbs or more you need the weight distribution hitch.
My tow package is toward the upper limit of the reserve Navigator. With the weight distribution properly adjusted it tows beautifully, I couldn't be happier.
Cheers