If a doctor tells you that your kidneys are healthy, does that mean that you definitley don't have diabetes?

No. You can have "healthy" kidneys with or without diabetes. If you are concerned about diabetes, please ask your doctor to test you for diabetes. There are many tests to confirm the diagnosis.
2 separate problems. Diabetes is the disease that is affecting Insulin producing cells in the pancreas. It will affect on how well your body handling/regulating carbohydrates/sugar from your diet. Diabetes can cause dysfunction on many organs including your kidney. However kidney problem is not equivalent to diabetes. There are many other things that may injure/ affect the kidney function beside diabetes.
No. Diabetes deals with the Insulin secreting cells of your pancreas. Diabetes can cause kidney damage. But kidney damage is not the cause of diabetes. I agree with holly's answer. There are other ways to test whether or not you have diabetes. If you are conned you should talk with your doctor about them.