Will the dies I already have work in the dillon?
Yes. Some dies are a tad on the short side, but you can put the locknut on the underside on the underside of the toolhead in most cases to get the length you need. Generally all dies are 7/8-14 thread so all major brands will work. They just have to be long enough. I've got serveral sets of Hornady, RCBS, and Redding. They all work on my 650. I've used Lee factory crimp dies too.