I had to do the same thing for my tiny toy poodle...gave him in-home dialysis for over two years. He did better with it than I did! As for diet, my vet just told me to let him eat whatever he would eat...so I did. And I never felt bad that he preferred boiled chicken breast over anything else...and I gave it to him!
I guess my advice is to follow your vet's instructions...and good luck!