For noobs it might be good to expand on two instuctions in the OP (i.e. how to get plugins working after updating from 64bit to 32bit build).
How to "Delete your old packages directory":
System -> Appearance -> file lists -> show hidden files and directories and allow file deletion
System -> File Manager -> add source (call it "Root") and browse/add the location:
Then open it, long press any file there and choose "Select all". Then long press again and choose "Delete".
How to "Refresh the repos":
Delete this file: /userdata/Database/Addons20.db
System -> Addons -> press left to bring up the side menu then click "Check for updates"