The factory cd player should look like the one in my car here, except instead of black face it would be gray.
The ERR problem usually means the mechanism that reads the cd'* has failed. When I took mine apart, I found this to be the problem, and had my mechanism rebuilt. This is the only thing that can be done, as far as fixing it.
The units themselves are old, while mine is a 1990, the circuitry inside reveals dates of 1986 and 1987.
When fixed, pressed, store bought CD performance will be fine, but CD R performance will never be what it is in newer cars, and forget about CDRWs.
Instructions I used:
When you take the unit apart, be VERY careful not to break the plastic clips that hold the faceplate to the radio chassis, I did this and had to epoxy them, and they are fine now, but its a pain that is easily avoided.