Ditto on everything folks have already hit upon. When we drove down to Rice the back of our pickup was packed full of stuff that we ultimately never used!
But...take a small hand vacuum because stuff sort of settles out..dust, fibers from the carpeting, etc after the first fifty miles. You might want to find a camp ground near to Rice so that your first night camping, you can run everything, check everything, and if it's not right, you aren't too far to turn around and go back for Casita to fix it.
You will receive a packet of literature that tells you how everything works. The fridge, hot water heater, etc. Mail in all the warranty cards ASAP, ESPECIALLY the one for the Dometic refrigator. In the teeny tiny print in the Dometic Refrigerator manual it says you have only TEN days to mail it in from date of purchase (they will want a copy of the sales receipt, too) in order for them to honor their warranty. Ten days isn't much when you're on the road, but do get it in the mail within the ten days.
Your propane tanks will be empty upon purchase. They won't fill them at Casita. I have no idea if the tanks have been properly purged. I suspect not. But they will tell you where to get the tanks purged and filled. There's a propane supply place just a mile or so up the frontage road and turn right that gets a ton of business from new Casita owners.
If all this seems a bit overwhelming, a bit too much information, it's okay. Take the information from this thread, make a list and it will go easy after that. It's just camping.
You are going to love your Casita, especially if you've been tent camping. The Casita is a very comfortable, well appointed tent on wheels. You will appreciate it best when it's raining hard and you are inside, warm and dry. Even more so when it's midnight and raining, and you have to use the bathroom. Then you will appreciate it even more! (trust me. You the Man of the Family might not think this important but I promise you, a bathroom will make your wife happy. )