Tracy,
so sorry to hear about your dog (it is Gatsby rt? not Gus). Unfortunately some of those diets don't work (which one was he on?). There is a technician at my practice that gets stones and every year he has to have sx (surgery) to remove them-nothing he will eat will prevent his stones from forming that is just the way it goes.
I definitely would spend the money-this is a fixible problem and he can live a normal/happy life for many more years to come. If it were something terminal then I might have a different opinion (last night I had a 16 year old lab in with a bleeding spleen that was most likely a malignant tumor and they wanted to put her through extensive sx-I think that is wrong but I had no say in it b/c I was not the referring vet.) So go for it!! My mother thinks I am nuts b/c I spend lots of money on strays-but she isn't the one that has to euthanize them-easy to bitch when you are not the one that has to make that decision and actually carry it out.
Let us know how he does
