My cat had a dental last year when he was about 19 - he had the blood tests before hand, these tested kidney and liver function. His liver was showing a little elevated so my vet put him on a drip overnight to make sure he was well hydrated and prepared for surgery, and then did the op the next day instead. I remember on here being advised that due to his age, to make sure they use rapinovet as the anaesthetic, which they were, and Sooty absolutely bounced back from surgery.
He had obviously been in some discomfort for a while and instead of being groggy and whiney after the anaesthetic, he was a "new cat" almost straight away! He leapt out of the cat carrier that evening and ate normally pretty quickly. The vet had taken all his remaining back teeth out but after several days he was back eating dried food again without a problem. He just had antibiotics for a few days afterwards but that was it.
I was warned that they can sometimes dip again over the next few days but he never did; we really thought that we were going to lose the old boy through the op but thanks to my brilliant vet, we had another 10 months with him
Good luck, please let us know how your little darling gets on!