You can download a copy of the factory service manual, which will include the wiring diagrams, from
www.fordcds.com. The site is free, but they certainly appreciate donations via PayPal.
I suspect the door ajar light is the rather common for Ford problem of a sticky pin switch which is located internal the door latch assembly. I suggest applying a good electrical contact cleaner spray to the door latch assembly and working the latch a few times (open and close the door repeatedly). Ideally, if you have access to Caig brand DeOxit and PreServ It, use the DeOxit as the cleaner and the PreServIt to protect the switch contacts and you should be good for quite some time.
-Rod