EDIT: No matter how many times I try, I cannot seem to get this video to work - https://www.youtube.com/watch?v=Te8u3qguxew
In my experience, the worst thing to do for interviews is to prepare too much. Don't overthink what you're going to be asked, etc. Because, chances are, everything you think you planned for will be completely skipped by.
This is an internal hire by the looks of things, so you're already known by the company. They know your work ethic, behaviour patterns, and productivity levels. If you were invited to an interview for the promotion, that means they like what they see, if it was open so that anybody can try for the interview, that may be a little more difficult.
Management skills are typically softer skills, so you'll have your work cut out proving them in an interview, if they haven't already selected you. Also, look at the managers in your company: can you do what they do? Would you WANT to do what they do? Sure it's more money, but management jobs (especially mid-level managers in larger businesses) are fucking boring jobs - emails, mindless meetings, and office politics with other middle-managers who are all competing for the next rung of the ladder.
Also, fyi, if you're as good at your job as you say, you might not get the promotion simply because they don't want to lose you at doing what you're doing. At my firm, bad programmers become managers, good programmers become architects, and "distinguished engineers" (who sometimes end up on more than the managers)