Is there any reason why I shouln't get my older cat's teeth cleaned?

My cat has the worst breath. he is 12 years old. never had a dental but I am scared because they have to use anesthesia and he is old. I had a friend that said her cat came out of anesthesia with some sort of damage and died shortly after within a few months of struggling with motor skills. I am reading that dental health is sooo important and if left untreated can lead to other medical problems. He has lived this long happy and healthy and I'm worried that something bad might happen since he's so old. What should I do? he has the death breath and it's smells so bad I know he's got some major plaque build up. And if I do go ahead and get him the dental, how do I keep his teeth good enough that I never have to do this again? It's not like I can tell him to go brush his teeth every night before bed and I'm sure I'd have my face scratched off if I tried to do it.