Scanner works as Brooklyn said...
The wire thing is as follows:
http://www.therangerstation.com/tech_library/OBD_I.html
Scroll down to "Test Hook-ups" and jump a wire across as shown between the single connector and the top right hand one. No need to hook up a voltmeter or test light as shown. Just hook the wire, then get in the truck and turn the key to "on" and wait for the flashes.
I think judging by your questions that maybe a code scanner would be the best bet for you and your experience, because if the codes aren't read correctly or missed pulled you'll miss a diagnosis. Once you do it, you'll wonder what the big deal was, but maybe a code reader would be a better option for you.
If you're brave, from Ford Fuel Injection:
How to Prepare for the Self-Test
To check for codes without buying a code reader is simple. If your EEC is wired correctly, the engine light works, and there are not any electrical faults in the vehicle you can get the codes out of your EEC.
Turn key to OFF.
Get a length of wire that can connect the STI to the negative battery terminal or body ground.
Ground the Self-Test Input.
Get some paper and a pen.
Get comfortable in the drivers seat.
Try to keep your self from getting distracted from here on.
Turn key to RUN.
You will hear some relays engage and the fuel pumps prime the system. This is the EEC beginning the test.
When the fuel pumps stop be ready to count!
If you'd like, I can take some pics for you, and I may do that because this topic comes up so much I can't believe there isn't a good, final write up (I found the supplement thread) about this with good pics instead of the MS Paint pics- unless I'm missing it.