The CD player on my Pioneer XR-A600 has not worked for a while. It says it has no cds when it has. I have had i fixed before but it cost over 100 pounds and hey just put a new cd unit into it. Could easily fix and change this unti myself.
I feel sure it just needs a good clean inside
While I'm not familiar with that particular model, you are correct in that it most likely needs either a good cleaning or the lens on hte optics assembly has fallen off. The problem with these particular units is that they are not easy to disassmble or reassemble. This is not a repair I would attempt unless you have done these before. Try using a "wet" CD cleaner first. This may fix it.