how to replace lock/handle rear hatch 1990 APV

I have a 1990 APV with a busted rear lock. For years we have opened it with a screwdriver, but that is no longer working. I have read on the forums how to get the door open (through the speaker port) but, am not sure what is required to replace the lock if I am successful in getting it open. I bought the AC Delco replacement part but, I would kind of like some idea what I am in for before I pop the hatch. Any help?