I got my cat from the RSPCA when she was 13 - she had just been diagnosed with kidney disease but, with the right kidney diet food and the occasional blood test to see how she was she died last year aged 19! I think I was very lucky but as far as I know there are 2 types - 1 you can give kidney diet to, the other a pill every day. Either way, it's doable and helps them alot. Her coat shone and she became a different cat after that, it's not a death sentence (depending on how far advanced it is obviously, but she had apparently seemed to have it for several years).

Take the advice of the vet and practice giving them their pill - stroking the throat has always worked for me, also being wrapped in a towel so they don't freak out as much. They will never like it, but they soon start forgiving you for it much faster when they realise it's over much quicker if they don't try to get away.