What are the symptoms of the problem?
Unless you know for sure what the problem is, the very first thing I recommend is that you verify the power supply is OK (if you have a meter).
The CD7 units may have used different CD drive types. To find out what yours has in it you'll have to open the case. Do you have any idea whether it's a drive or electronics problem (no kids putting peanut butter in the drive, etc.)? Once you find out what type of drive your unit has you can look around for a replacement.
My CD7 has a 2x proprietary Panasonic drive. I believe that the CD7 could also be configured to use a Sony proprietary drive. If the electronics in the drive case are bad they'll be easy to fix, it only has one IC.