The AKC Canine Good Citizen test really tests that your dog knows some basic obedience and does not have any bad habits, such as jumping on people or barking at other dogs. You can read about what is tested and what the individual test portions are on the AKC website at AKC's Canine Good Citizen (CGC) Program
The actual test can vary some, depending on the person who does the testing. Some test all dogs separately, some will test in a group. It really depends. But the basic portions of the tests will be the same, and the AKC website will tell you what is tested and what you can expect.
With any dog, you don't need to do lengthy training sessions to build even complex behaviors. It's much more fun for the dog if you are able to work five minutes here and five minutes there, rather than having them in classes of 1 hour with other dogs around them. Some of the best stuff I've taught my dogs were things we worked on during commercial breaks on TV, a few minutes each break.
You can go very far training by yourself using a clicker and rewards. A reward does not always need to be a treat, you can also use a toy, or even a "life" reward (such as letting the dog outside after making him sit, etc.).
If you have never done any clicker training previously, it helps to work with an experienced clicker trainer who can show you how to use the clicker and how to get your timing just right. Timing is the most important part of clicker training and the hardest thing to learn. (Well, timing and having enough hands to hold leash, clicker, and reward at the same time!)
You could try to see whether there are any Karen Pryor Academy trainers in your area who would work with you one-on-one, keeping your training limitations in mind during the process. (It may be easier to find a trainer that can work with you in that regard if you look for one-on-one training rather than a class.) You can look for Karen Pryor trainers at Find a Great Dog Trainer | Karen Pryor Academy
Some of those Leerburg videos are fantastic, too, but they are not cheap. I have "The Power of training dogs with Markers", "The Power of Training dogs with Food", "The Power of Playing Tug with your dog", and "Focused Heeling" and they're all very good and helpful.
One of the features I like most on the Michael Ellis videos is that they show you actual people attempting the techniques for the first time with their dogs, and you can see what they're doing wrong and how to avoid the same mistakes.