So sorry you’ve had this news; I’m sure it must have knocked you, and it’s no wonder you didn’t absorb all the information to start with.
Kidney problems are quite common in Leish dogs (from both damage caused by the parasite and the drugs used to control the parasite), so it’s quite high on my radar. I’ve not had to deal with it myself, but on the FB group I’m a member of, there are quite a few dogs with kidney issues. From what I’ve seen, in the earlier stages, it’s relatively easily manageable with specific renal diets.
As
@SwampDonkey says, it’s good that you now have numbers that you can use as a baseline as you tweak things; that will let you know if they are working.
I’m glad your vet seems switched on and friendly; it’s so important to be able to trust your vet and this one sounds like a good one.