well if its like a 97 wich i dont see why it wouldentbe there are 4 small holes in front of the head unit..
if this is the case you will need some very stiff wire (welding rods TIG work best for me) and press all 4 through about 2-2 1/2" this will release the clamps that are holding the unit in. these can be very tricky to release.
from there you can try to wiggle it out or get 2 needle nose pliers and pull... if your arm will fit drop your glovebox and weasle your arm to the back of the unit and push it out..
as for wiring 1992-93 Ford F Series Stereo Wiring Information
this is it... but sometimes it can be very hard to tell 2 wires appart.