I would buy the trailer. Even if you opt not to use it for your max possible load. You mentioned just a few trips to the dealer for periodic service would pay for itself.....You dont need to take an implement and the loader for this service. Plus, you would have for the future, if you ever do get a bigger tow vehicle. Plus, lets look at the numbers for a minute. With the 7200 GVWR - 5350 curb weight, your expedition can haul almost a ton. With the trailer capacity at 10k and weighing 3700, it can haul 6300. So take your 7000# tractor and position it so you have at least 700# tongue weight. Then you will have 1k or less on the trailers axles/tires. and still be within the 7200gvwr of the expedition. Only think you are over on now is the 10k hitch. you would be over by a whole 700#. But some hitches are rated a higher number with a W/D hitch. So it may just be a matter of getting one. Or even if you have to spend a few hundred on a new hitch all together, its still a good deal if the trailer is in good shape.