If you decide to buy another Windstar, the head gasket problems in the 3.8L engine were largely fixed with the 98 model. Also, These transmissions will not stand up to towing anything over about 1000 lbs, and last a lot longer of the driver doesn’t have a heavy accelerator foot. The Windstar transmission absolutely needs the fluid changed every two years or 24k miles (or so). To minimize your chances of a head gasket problem, you must be especially vigilant for any cooling system problems and take care of them before the engine has a chance to overheat. Since your engine made it this far, if there are no other warning signs, there is no reason to believe its demise will happen in the next 15k miles. I would classify the steering problem as a repair. However, with an 11 year old vehicle, most of the work you had and need to have done I would classify as maintenance. It is true that the Windstar has some weaknesses - including the head gasket and transmission.
