Fennel I think it is misleading to describe this as kidney disease, compared with those with severe kidney malfunction. Kidney function does decline with age, but the figure you quote, similar to mine, is very much borderline and you are unlikely to have any symptoms of failure because you still have more than enough kidney capacity to meet normal parameters. My doctor was entirely off hand about it.
Looking at the kidneycare site, the recommendations for healthy eating are standard, as are health warnings about blood pressure and cholesterol. The need to reduce potassium and the like is very specifically aimed at people with kidney failure or severe kidney disease.
I would just wait until you see the doctor. If it was really serious, they would have called you in for an immediate appointment