Hi there!
As you know the positions of WDW planners are few and far between, based just on the fact that there aren't that many positions and there isn't a whole lot of turnover. Your best bet would be to get a lot of hotel and conference center experience. A lot of the planners have worked in events for decades so you are already starting off at a bit of a disadvantage. Also like most of the areas at Disney they hire almost exclusively from within. So you're going to want to get a position with Disney somewhere, preferably in one of the conference centers as a banquet captain or even better a catering guest service manager.
As far as a degree, most had them in hospitality, but not all of them. I would say they stress experience over actual degree for certain.
If you are talking about just as a Weddings PI then the criteria is a little less stringent. As I said I had about 3 years hotel and guest service experience. I also have a lot of computer experience (about an 8 on a scale of 10), which came in handy and they did ask about what programs I worked with during the interview. They work a lot with Seibel, Disney Sales and Catering (and internal program) and the Microsoft Office Suite.
Hope that helps! Good luck to you! :wave: