You´d be disappointed if you´re looking for a direct replacement for the CDROM2 - the CDR-35 doesn´t work with the IFU-30, I can definitely confirm that - I´ve tried to get it to run. It plays music fine (though you can´t access it via PCE/Menu/Buttons), but only if you push buttons directly on it.
I own a working unit, it is internally different in electronics, which you clearly see when you compare them both.
If you´re looking for a spare parts unit, I´d go for it, especially when it´s still fine or hasn´t been tampered with.