John, sounds like you're pretty handy if the sink and A/C unit don't intimidate you. The problem was probably caused by the ice maker not being winterized properly and the water line in freezing and cracking. I personally would look into West System (
Epoxy by the Leading Epoxy Manufacturer | WEST SYSTEM Epoxy) and see if I could repair the sub floor instead of replacing it. I just went out and looked and my 1986, and it would be a time consuming endeavor to pull the cabinetry out of mine to allow access to replacing the sub floor. Seeing as you're in my neck of the woods, you're more than welcome to look at mine anytime to see what you would be up against.