Sorry to hear about your GSD. They are prone to the type of thing you describe as they get older. I know of one that successfully used a wheeled cart for some time after his back legs failed, but it sounds like she is beyond that stage.
Know that a Basenji will be 180 degrees different from what you are used to. A GSD will want to please you, a Basenji will please itself. Training requires figuring out how to motivate the dog. But if you have been reading up on the breed, you know that. In practice it can be a bit different than in theory! Patience and a sense of humour are definitely required. But they are an acquired taste, and once you have had one you will know what I mean. Speaking as someone who has had a Border Collie at the same time as two Basenjis. My BC would do anything for me if he could figure out what I wanted. My Basenjis were more like "What's in it for me?"