I'm afraid this is not something I have any experience with, so I do hope someone else will be able to give some advice.
As a general comment.......I do think you need a little time and a bit more information before you opt for more surgery, although in the end you will probably find it is best to take the specialist's advice.
I would suggest when when speaking to the Specialist you have a list of whatever you want to ask written down, and you write down what he tells you the latest scan has revealed.
If they want to operate , check out if the surgery is urgent. If your boy is being kept comfortable then it may be worth telling them that you would appreciate a little time to make a decision.
His last surgery is so recent, I think you need to be sure of all the facts in your own mind before you can feel right about agreeing to more.
Cavaliers......Faith, The Ginger Tank and Woody.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.
Remembered with love......... Tommy Tuppence and Fonzi