I'm a little late to this thread and the other posters have already made it pretty clear that the salesperson exaggerated greatly on this list of "required" items.
To respond to the OP's question regarding Lee dies in the Dillon press: The Lees will work fine, and produce the same ammo as Dillon dies; however, Dillon dies are radiused a bit wider than most at the mouth of the die to allow easier use on a progressive press. Your turret only slides one round into one die at a time, so a little misalignment is easily corrected as the round starts in. On a progressive press four rounds slide into four dies at one time. Familiar with the engineering concept of tolerance stacking? One round is off a little this way, another that way, another a third way, and your press suddenly won't go until you manually free up the rounds.
Not a deal-killer by any means, and you'll find many who use other dies on a Dillon. But I use Dillon dies on my Dillon 550B for this reason.