Full timers almost always top out higher than part timers. By the way your union steward can't do anything to "get" you a full time position. It's all about average cumulative hours within a given period, or accepting an automatic full time position (department leadership).
Going full time in UFCW 1529, delta division nets you at minimum $1 an hour raise. It technically bumps you to the nearest full time tier of pay that nets you at minimum $1. But can be higher. For example, I was already topped out for part time pay when I went full time. The nearest tier was $1.50 higher than the top out for part time, so mine was that much.
In the Atlanta Division, you must outlast the total time period the dinosaurs lived before their extinction occurred, in order to get top pay with full-time. It scares people away because of how long you gotta work and sustain full-time, to reach top pay.
The unfortunate thing is that you will not be able to get a full-time position unless one becomes readily available. Keep your eyes open for bids on your notice board in the break room or ask your supervisor if there is one available. Since you have been working for 13 years, you should have more seniority than most (maybe not all) which will allow you to get the promotion before anyone newer than you. Another thing to take into consideration is work experience. If someone has more work experience and is better suited for the job, they may get it. Just make sure that you know as much as you can about every little thing to give you that extra edge.
As for pay, it depends on your department. Some positions have max pay rates for both part-time and full-time employees. You may want to talk with your Human Resources department about if your pay rate will jump up (if your department has the full/part time pay rate caps).
