One thing that you will find the Liberty's gas mileage is not as good as the Cobalts. I average about 15-17. The worse I got was bout 13 and the best 21.5. You have to realize it is about twice as heavy.
As far as driving it over the sand: Tire Gauge, Air compressor, Tow straps, Shovel, Tow hooks recovery hooks on the front and back of your vehicle, Fire extinguisher, couple of boards and/ planks of wood. The hotter and drier the sand the more airing down you need to do with your tires.
As far tune-ups it can vary dependent on your driving; I usually rotate the tires when I change the oil @5-6K, also check the air filter and change very 20-30k as well as the "in cabin" filter behind the glove box.
Review some the posts and threads and feel free to ask any questions.
Welcome to the club