Welcome to the forum. See if you can find an owner's manual for this particular rig and read it. You might be able to borrow one from the rental place and photocopy it, and take the copy with you. Since you have indicated that you have "never driven anything like this before", have you done any RVing? If not, there is much to learn, that can't be put in a couple of posts. You may need to search the forums for beginning RVing.
A couple of quick things. The RV is usually much wider than a car, so you will need to work a bit harder to keep it fully in your lane. So, as someone told me when I started out, "hug the yellow line" until you become familiar and comfortable driving the rig. The rig is also taller and heavier than a car. Make sure you keep the rig within the Occupant and Cargo Carrying Capacity of the unit, and make sure (beforehand if possible) that your chosen route will keep you away from low bridges. Memorize your height, width, and weight limitations before heading down the road.
Examine the tires of the rental unit at pick up and make sure there are no cracks in the side walls of the tires. Frequently check the tire pressure on all tires and make sure the pressure is proper for the load you are carrying. Blowouts are not a pretty thing in RVs.
Make sure the rental company goes over how to dump in the rig. Remember, black before gray. Take some gloves that you can use and not worry about getting some sewage on them. Consider disposable gloves.
Find out where the electrical panel is, know how to reset any breakers, and take a few spare fuses. Learn how to charge the house batteries. Learn how to operate the generator (if any).
Learn where the propane tank is and the main shut off valve are located. Know what appliances use propane. Learn proper propane filling procedures for the unit.
Check the batteries in all alarms in the rental.
I hope this helps a bit, and hope you enjoy the 4 corners area as much as we did. Have Fun!
