I would change the power steering fluid......it calls for a "Type F" transmission fluid.
I have Redline Synthetic Power Steering fluid in my '96.
The windstar is known for cooking the power steering fluid.
There are a number of posts on here about flushing the power steering fluid.
Also, I would change the oil.......and take a sample and send it to be tested.....You are looking for any coolant that may be getting into the oil.
http://www.blackstone-labs.com/
Will get you all the information, and a free sample kit.
They will tell you if you have coolant in the oil.
Before spending any money on the vehicle......verify that there is not coolant getting into the engine oil.......as the repair will cost money.......and not repairing it will cause total engine failure.
I am not trying to scare you.....just trying to cover a potential problem.....so that you can get it solved if it is present.
For the '96 3.8L, common causes for coolant into the oil are the front cover (aka timing cover) gasket.......Major labor to replace that gasket.
Also the lower intake manifold gaskets are prone to leak.......buy ONLY genuine FORD / Motorcraft replacement lower intake manifold gaskets to make certain that you get the latest improved gaskets.
The head gasket is NOT a high failure item on the '96 and newer windstar....It was high failure on the '95, but they made changes after that year.
I had a very slight seapage at the front cover gasket....and have kept it sealed for 3 years with Bar's Stop leak.
I plan to keep some in my coolant all the time.....The silver bottle is easier to use than the original pelleted type....but both work.
They sell tablets and powder also.....which I plan to try next time.
A very good practice when getting a new-to-you vehicle is to change all the fluids.
For the '96 3.8L windstar.
Oil, 5W-30 OR 5W-20 (as per recent TSB).....I use a synthetic....Mobil 1 is good.
Transmission fluid Mercon or Mercon V (as per recent TSB)...synthetic is HIGHLY recommended, as is an auxilary cooler
Coolant, traditional green (hard to find now..... Motorcraft green).....I flushed mine and replaced with G-05 (motorcraft gold, or Zerex G-05)
Brake fluid, DOT3 fluid......bleed a libral amound from each wheel....until it runs out clean.