My DH didn't spay our Min Pin and she developed pyometria at age 11. We had no choice but to spay her and correct the infection, but I was concerned that she may not make it through the surgery (which she did). She is old and has cancer. They did the bloodwork and all the pre-tests and charged us around $450 which we got most of it back through our pet insurance.
IMO, it's a decision left between you and your vet. If you're not comfortable with the vet's recommendation, get a 2nd opinion.
Good luck and keep us posted on what you decide to do.
