First things first.... try a new CD to make sure the ones you are using are not to blame.
Otherwise..... just changing out that drive can be tough sledding w/o paying a butt load of cash. There's another thread currently asking similar question.
Others would have to comment on potential repairs.... I don't have info there.... but I wouldn't hold my breath. Maybe look for a used unit (entire head unit) on eBay or Craigs List or ??? (maybe search for threads here as well...trading post category)
I'm guessing if it comes to replacing that unit, you'll be better of with an aftermarket upgrade.