I would try the solvent based fuel system cleaner.
There are a couple of professional strength cleaners, though I have not tried them.
The fuel injectors on the windstar tend to build up crud on the spray end.....and the Berryman's is the ONLY cleaner that I have used that worked on this.
Chevron Techron, Redline Fuel System Cleaner, FP60, and other products did not work for this....although the rest of the fuel system stayed very clean.
Cylinder #1 is on the rear bank, driver's side.
Cylinder #5 is on the front bank, middle.
So you are seeing a problem on BOTH banks #1 and #2.
As the 2 cylinders are on the same coil....you might verify that the switching INTO the coil is working.
That comes through the plug on the coil, from the PCM.
Fuel pressure is a possible, and the best way to diagnose this would be to have the fuel pressure monitored at the fuel rail (there is a connection on the front, center of the fuel rail for this), while the vehicle is being driven on the highway.
Then, if the fuel pressure takes a drop when the misfire happens, you can suspect, most likely, a fuel pump issue.
That said......have you changed the fuel filter lately?...much cheaper than a fuel pump replacement, and routine maintenance anyhow.
If you come down to a fuel pump issue.
There have been posts about the fuel pump relay in the power distribution box causing intermittent to solid failure of the fuel pump function.....also MUCH cheaper and easier than a fuel pump replacement.
This relay is something that you can easily purchase and replace yourself.
There is also a "sock" filter on the fuel pickup part of the fuel pump assembly,...but that also requires removal of the fuel pump assembly to get to.
Removal of the fuel pump requires that the fuel tank be dropped.....so I would recommend you eliminate the other, easier items first.....including the wire connections to the fuel pump.
The only thing that I would expect with an oxygen sensor would be if the mechanic crossed the wires when re-connecting them, connecting the wrong sensors to the plugs.....very easy to do, but still not consistant with your symptom.
For this reason, I tend to agree that your oxygen sensors are most likely fine.
I replaced my upstream sensors with genuine motorcraft at about 155K miles, after having had lower intake manifold gasket leaks that leaked enough to leave a green stain on one of the sensors.
In my case, I did not notice any change at all in engine performance or fuel economy.
Yes, the replacement sensors are working just great, but the old ones were still good.
When you get codes like P0171 and/or P0174, that is the oxygen sensor(s) reporting a lean condition, which is almost always a vaccum leak.....causing too much air to enter the intake, and the PCM is not able to compensate for it.
There are other codes that would indicate a bad oxygen sensor, like indicating a problem with the heater circuit, or slow switching rate, etc.
In short, the oxygen sensors on the windstar are very reliable, and rarely fail.