I have the OEM Repair CD and the Mitchell CD for my Windstar that I bought off of ebay (about 10 each). I also have a 96 Chiltons and a 95-2003 Haynes. That's where I get all my diagrams.
I order the parts online my name and usually do not need a ford part number. I go totally aftermarket if I can because I will not give Ford any more $ for this vehicle.
Other than that, you can call a dealership and get the part number. I have had actually good experiences with them.
The other people on the forum are way more experienced than me in this area.