Unfortunately, every unit is different in terms of disassembly.
Usually, the top and bottom cover plates are removable without too much trouble.
Standard practice places the CD mechanism towards the top, and accessible by removing just the top cover.

I have never had problems with the lens getting out of alignment when cleaning. Just be gentle with it.

Try testing it before full reassembly. Might save you some trouble if a cleaning is not going to do the trick.

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1986 300E 5-Speed 240k mi.