Hi Lucy - I think this is brave of you.
Practice will definitely make all the difference. Also try to be strategic in your routes and timing. For example, pick routes that will include larger truck stops or turnpikes for fueling, so you don't have to squeeze your RV into a tight little neighborhood gas station. Also avoid smaller surface streets until you feel more at ease.
I don't know if you're a visual learner or not, but try searching online (especially YouTube) for video tips. The "swoop" maneuver is a big help when it comes to backing a large trailer into a parking space or campsite.
Remember to breath and relax. If you can keep your emotions in check, you'll react better and it will be easier to drive and back into tricky spaces.
Good luck to you.