I'm sure others will have more to add but I'll mention a few things.
If the dealer does not supply a sewer hose with the trailer, you will need one (Rhinoflex is a very nice hose that comes with adapters for various sewer openings). Also make sure you get an electric plug adapter to step down from the big RV plug to regular 3 prong 20 amp. You want a fresh water hose (white is usual color) and a pressure limiter to screw onto it so you can't blow out the trailer's lines with too-high city water pressure. Get a couple of wheel chocks. Some short 2×4 or 2×6 pieces for leveling the trailer can be handy.
Inside, it's the usual stuff. Bedding, plates, cups, flatware, utensils, a pot and a pan (or more), towels, RV toilet paper, soap, etc. First things I added to my trailer were a towel ring and a paper towel holder. I want a small mirror before my next trip, too.
How many inches of drop? I could only guess. 6 or 8 inches or more? Maybe someone else has thoughts on it.