Will a nakamichi head unit( with cd button) be interchangable with a orginial Lexus head unit (with no cd button).

Is all that I have to do is change the wiring harnest or will I get away with running separate RCA jacks to trunk to cd-changer?
OR
Do I have to run a new wiring harnest?

Are there any changers(other then orginal) that will work with nakamichi head unit?

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