Wow, thanks for information above. I'll definitely get out of the airport and do something--doing it myself instead of a tour is actually my usual methodology, but I figured why not be a lazy slug for a change and let somebody else do the thinking for me.

As for tour times, I was looking at this tour (4 hours) and these tours (5 hours) which seem to be by a commercial agent and I've found another as well (Hana tour).

I will definitely want to get back in time for a shower and clothes change before that flight to LAX. I hear there are free showers on the 4th floor?? Neck massage at reasonable cost??