If you decide that you want to surrender him, then you may want to start a thread in the forum for Yorkie Rescues and New Homes Needed. Some people on here do private rescues and may be willing to take him. These people have special arrangements with their vets and may be able to get the surgery done for less.
Or you can try this one in your area:
http://www.unitedyorkierescue.org/faq.shtml#15
SURRENDERING
I need to surrender a yorkie. What do I do?
Click on the Immediate Home/Placement link on our home page to contact our Foster Coordinator. Please provide your name, location and information about the dog, including age, health and any behavioral issues if possible. Someone from your area will be in contact with you soon thereafter to make arrangements or refer you to another rescue if we do not have members in your area.