In addition, since you have a senior cat, find out if they do a senior panel first. This will most likely include blood, urine tests, possibly chest/body xrays.
These tests are to make sure your cat is in good health (aside from FD) and will be able to handle the anesthesia.
Oh and ask what kind of anesthesia they use as there was a very recent recall on ketamine
see this link:
http://www.felinediabetes.com/phorum5/r ... ?8,1962009
And you may want to bring the information in, in case your vet is unaware of it.
Also for your own level of comfort and understanding, ask the vet the step by step procedures used when doing dentals. Who puts the cat under, who cleans the teeth, who is monitoring the cat, what happens after, where is cat placed and who monitors.
Also ask if they use pain meds before, during, after the process and which ones they use.
As there is some controversy on that as well - read here:
http://www.felinediabetes.com/phorum5/r ... ?8,1867651
I say better to be informed and fully understand what is happening then to be hit with surprised.
Finally, ask them to give you a cost estimate - they ought to be able to do that and will probably tell you it's figured out higher than anticipated, just in case.....