Regarding the irish section of the interview, I wouldn't class it as tough (did one or two myself for various panels).
Mine consisted of reading a passage aloud in Irish, then translating what the passage said (not specifically word for word, but a close approximation at the least), then a general conversation similar to your LC irish oral exam - general chitchat, if you head off on a particular topic (say for example you mention you like travelling when asked about what you like to do for fun) the examiner will usually follow your lead and ask you where you've been, how you found it etc.
Hope this helps a little.