1990 Mercury Topaz

Here is the Problem:  My girlfriends factory radio did not work, so I went out and got a Sony Fm/Am Cassette Stereo XR-1750.  I installed it myself and before talking with my brother cut the factory wiring harness out and threw it away.  I got one from the junk yard and rehooked it to the factory wiring.  I have a Metra Wire Harness for the Ford/Mercury which is fine.  I have everything hooked up, but now the Problem.  I have pulled different wiring diagrams from different web sites and my problem is this:

Unless I hook the illumination wire from the Metra Harness upto the 12 Volt Batt/Memory on the Metra/Sony Wires, than I have no power to the unit.  The next problem is that I still have no memory at the unit.  I can put all the Radio Channels in, and when I go away for awhile and come back, nothing is in the Memory. 

The other problem is according to many wiring diagrams, there should not be a illumination wire for the Mercury Topaz, there is a dimmer, which I don't have hooked up, because when I do my lights are on all the time.