If I stopped smoking and change my diet should my kidney disease reverse?

I don't know. The source of your kidney disease is unknown thus it is difficult to comment accurately. That said, I have watched kidney function improve in my office on a regular basis. There are as many ways to approach the problem as there are causes for it. Smoking cessation is a no-brainer. Just stop it: it kills you and your kidneys. Phosphatidyl choline, a nutrient in egg yolks, improves kidney function.
Yes. As smoking directly affects the blood vessels the answer to your question is yes. As a healthy diet; along with an appropriate exercise regimen (walking for example) with lead to a healthier body the answer to your question is again yes.