The LR3 is rated to pull a 7000 pound trailer with a 550 pound tongue weight provided the trailer has brakes and the ball height is positioned to keep the trailer level and within a certain vertical range. All of this well spelled out in the owners manual. Your choice of an Airstream 23D exceeds the recommended tongue weight, not by a large margin but enough to elicit concern. If you follow the factory recommendations you don't need any additional towing aids and they are not recommended. No reputable RV Dealer (especially an Airstream dealer) is going to let you drive off the lot unless your vehicle is capable of and properly prepared to tow. With regard to the tongue weight, I would discuss this issue with the dealer. Note that the Airstream 23FB has a tongue weight of 467 pounds, within the range of the LR3, while your 23D has a tongue weight of 720 pounds (galleys weight more than bunks!). Of course, once you load all of your personal gear, both of these numbers will change. The only way to really know the tongue weight is to pack it up and weigh it, not a very practical option for something that weighs 500 pounds!
I have towed boats that weighed 7000 pounds and camper trailers at 5000 pounds all with the factory hitch and never an issue. My measure of tongue weight - if I can lift it, its within range. Again talk to the dealer but I suspect that after you load the portable canopy, camp chairs, BBQ grill, fishing equipment, and all the other things we take camping under the aft bed in your 23D the tongue weight will go down. With judicial loading, I think you can get the tongue weight within the range of the LR3.