As someone that was in your shoes almost 20 years ago, let me assure you it’s not a sure thing. Part 121 training is a different animal when all you know is the military way. I passed, but it wasn’t a cake walk. Jepp charts, phraseology differences (what the hell is a V1 cut... it was always an EFAR to me), not a lick of jet time, and very little automation familiarity compound a stressful situation. Do your part and know the stuff your supposed to know cold so that the “stuff” is manageable.