They should not have I-751 interview if youe GC is being produced. Take new GC and I-751 approval letter to interview and give it to officer when they ask to see GC.
Even if they were going to do I-751, they would then realize they don't need to.
Anything about your immigration, background and your spouse.
Remember dates, names, trips you took, places you lived at, placed you worked at. Know marriage date, birthday of your spouse and kids, where do they work or study, how you met.