Promotion opportunity within union setting

I work for a union company. I've been working as the assistant for my department head since COVID ended. My role isn't a staff position per say, but when they need an assistant I'm the first person th

I work for a union company. I've been working as the assistant for my department head since COVID ended. My role isn't a staff position per say, but when they need an assistant I'm the first person they hire. Typically the assistants move into the head position if they're interested, but there is still an interview process. Since it's been over 25 years since I've interviewed for a job I want to be prepared. I know the folks I'll be interviewing with pretty well already. So that's a plus. I think at least two others are interviewing for the job. Since, all my references are my current coworkers and the union reps what other things should I think about/consider?