Dillon will be fine with the situation. BB, his coach, had the respect for his starter to give Corey a call and let him know they were taking a Running Back. Maroney's value to the team was too good to pass up at that point in the draft, it is, after all, a business.
BB knows that Dillon was disappointed with his performance last year and is busting his butt to get into exceptional shape for this year. Corey, for the first time in his career, has hired his own personal trainer to work with him for improving speed, strength and durability (he's running up sand dunes ala Walter Payton to get his power back and legs of steel). The man is pissed off at himself and now realizes that combating age requires increased effort.
He is also a professional on a very Team oriented football team. He will do whatever it takes to assist the newcomer because it is fully expected by his coaches, his teamates and himself. This guy will be the one who will give him some rest in a game so it's in his own best interests to help the guy that essentially can extend Corey's career by taking some snaps and keeping him healthy. Maroney is also going to realize that Dillon has a wealth of knowledge that he needs to learn to give him a fast learning curve for the NFL. They should work well together, the seasoned, grizzled veteran teaching the tricks and techniques of the trade to the new and respectful rookie so that they end up pushing each other to great heights.
Dillon's also smart enough to know that BB has always felt that competition is a necessary tool to get the best effort out of all his players. I also think all he really wants is to perform well and help his team to keep their winning ways. I doubt that he is satisfied with one ring so he should still be hungry. I don't think there's a problem at all. I think the ones with the problem are Pass and/or Faulk!