Most of the time, Buttons need Deoxit D100 cleaning, Optical need Alcohol cleaning, and Mechanisms need cleaning and lubing with White Lithium Grease (Tube)
Maybe easy to fix.
Image of an extended cleaning of the optical, under the top lens, (but most of the time, no need to go as far)
http://lampizator.eu/LAMPIZATOR/TRANSPORT/laser/Laserology.html
Sometimes I lurk on for some AS-IS good quality CD Players on the cheap just thinking I could fix it, but I have less and less use for a CD player.