Yes, check the CDs on another player. CDs sometimes get "disc rot" with age -- they look fine but won't play, skip or have distortion. It usually ties back to oxidation due to manufacturing problems. This is fairly rare, though.
For the player itself, it sounds like perhaps the lens has either gotten dirty or is out of alignment. Like any mechanical device, things do wear with age, or perhaps the settings weren't tightened properly when your unit was recently serviced and the lens is out of alignment. There is a lesser likelihood that the new laser unit has gone defective. In any event, if it is not the CDs themselves, it is time to go back to the shop for another round of service.
For the player itself, it sounds like perhaps the lens has either gotten dirty or is out of alignment. Like any mechanical device, things do wear with age, or perhaps the settings weren't tightened properly when your unit was recently serviced and the lens is out of alignment. There is a lesser likelihood that the new laser unit has gone defective. In any event, if it is not the CDs themselves, it is time to go back to the shop for another round of service.