Is diet very important to a kidney patient?

Yes. However, associated disease and degree of kidney disease would refine the answer. Diabetes for instance requires diabetic diet to protect the kidneys. High blood pressure would require strict salt control to protect the kidneys. Different stages of kidney disease dictate different levels of restriction e.g. Protein, potassium, and dairy restriction in advanced stages of kidney disease.
Absolutely . There are many dietary restrictions and recommendations for different kidney disease and the degree of disease. I recommend consulting with a renal (kidney) dietician regarding what type of diet to follow.