If you never take your dog to places where you want to take your dog, your dog will never learn how to be in those places.
First, identify the potential issues you may face. You know walking on a leash is one. How is the dog with strangers? How about small animals? Is it a barker over everything?
Once you've identified the potential issues, it's time to find solutions. The leash is easy - get thee to an obedience training course. Practice at home. In no time at all, your dog will understand the leash and so will you. Barking - try a water bottle to squirt the dog. The nice thing about shepherds is that they are eager to please - often a tone of voice is enough to convey displeasure and the dog will learn.
So now you've identified potential issues and determined action plans to retrain the dog's behavior. Now it's time to put it into practice.
Start by getting the dog used to the trailer. Have special "trailer only" treats and toys - the dog only gets these when it's in the trailer. Do overnight "driveway" campouts to get the dog used to sleeping in the trailer and used to nighttime sounds. Teach the dog that the trailer is a fun place.
Start camping small. A simple 2 night stay at a local campground. Choose NFS, BLM, COE, and reclamation campgrounds. These are usually the most dog friendly. Take your dog hiking on leash during the day. Do a walk through of the campground with the dog. Watch to see how it reacts to different things. If you see an issue, work out a way to fix it.
Don't be afraid to tell others about an issue. My Bat-dog has people fear issues. I let folks know that up front. I give them some guidelines "don't look her in the eyes, let her come to you, and don't lean over her". Most people take compassion and will go the extra mile to reinforce that people are not going to hurt her. This has changed her from a dog who wouldn't let a stranger come within 3ft of her, to a dog who can accept scratches and pets from most people (food will increase the odds greatly). Whatever the issue, just show people that you are trying to resolve it and they will be understanding (well, except a few folks).
During your first few trips, you'll gain a much better understanding of how your dog takes to it. You may find that the dog gets cranky after a day or two - that often happens due to over stimulation. If so, keep to 2 night trips until that eases. Then go to 3 or 4 night trips. The more you camp, the quicker the dog will adjust.
A final thought: I rescued a 3yr old akita. He had spent his entire life in a kennel in a backyard. He had never been on a leash. He had never seen a river, lake, flower, grass. He was fearful of men. When he came home with me, I started taking him hiking and for trips to the local park. Like Ferdinand, he loved to sit and smell the flowers. He loved to wade in the river and get his feet wet. He went camping with us and never had a problem. Had I taken the advice given by some here, he would have been confined to a backyard and never experienced any of these things he loved so well.
