Clean the inside of a 5 disk dvd/cd changer

the system itself was bought brand new for us after our house burned and for a long time went unused. we had a dvd player and didn't need it. Now we are trying to use it for the first time really in my son's room, and it turns and everything it is supposed to do except play. it clicks when reading the disk and I know from past experience that means either the disk is messy or faulty or scratched or the system needs cleaning or something. the dvds are new so it has to be the system. how do I clean it? can i get the stuff to clean it with at any dept. store? thanks for your input.