Gil, Spaw's heart surgery is a simple procedure. It appears he has too much heart and it conflicts with the curmudgeon attitude in his brain causing ulcers and bad tempers. So the doctors are removing part of the heart to try to bring him in line with his "attitude".

I predict the operation will be a success and he will heal completely. However I also predict he will continue to be a nice guy no matter how much they do to his chest.