@ InkedMarie,
As long as the pre-op labs are within normal limits and the heart sounds good, I wouldn’t worry too much. I would be more concerned about infection/pain and all that jazz that can happen with untreated periodontal disease.
My small breed had 2 surgeries at age 11, one was for a late in life neuter due to a testicular tumor. I declined the labs and signed the waiver.
The other was for emergency surgery due to bladder stones, labs were slightly off but it wasn’t a concern as this is often the case with seniors. He also had an asymptomatic heart murmur. Both times he came through fine and lived 5 more years.
They have dental specialists and geriatric specialists for dogs now too, if it would make you feel better to seek one out.
