So far as cleaning the laser lens goes, if using a lens cleaner CD doesn't seem to do the trick keep repeating the process a few times. Today I had to do it four times before the lens was passed as clean.

Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives This site looks useful, for those who can understand technical instructions. (Unlike me - I have to learn by hands on trial and error.)