Before you do anything else, make sure that you don't have too much free play in the clutch pedal. Too much free play will leave you with too little travel to disengage both stages.
Also, some 3000s used a 2 position clevis where it attaches to the throwout arm cross shaft. One position was for single stage use, the other was for two stage. See the owner's manual for more info.
If this all checks out, you then have to determine whether the disc is actually stuck, or if there is something mechanically wrong with the pressure plate not allowing it to disengage. If it is the former, there are numerous ways people use to "pop" a stuck disc. If it is the latter, better figure on splitting it.