I expect you'll have to disassemble it. Hopefully you can remove just the top cover with just a few screws and access the disc.
Regards,
Wayne A. Pflughaupt
What ManW said. Any pre-packaged system of this type is going to come with its own speakers. If you really want to keep your current ones for some reason (like it’ll be difficult to re-wire for them all), then another Panasonic is your best bet. Do your research to make sure they are still...