You'd probably be better off leaving everyone behind. When we switched from Sprint to AT&T, we got new numbers. Co-Worker just ordered, said it would take 21 days. Right now your choice is what carrier to pick.
^^^ Yes, you need to order the phone first, but if you want to keep the same number, it would be best to go into the store and do it. That's what the co-worker did to make sure everything was correct. Otherwise they'll assign you a new number. Obviously the stores are going to be packed tomorrow. If you can go today and pre-order, that would be better.
If you order with a new number, then you keep your old phone for a month while you tell everyone (you want) about the new.