Japanese used lens are usually in great condition and come with a 6 month warranty from the store usually. But the thing you'll probably find out sooner than later is that camera equipement is MUCH cheaper in the US than in Japan, even though it is made here. My recommendation would be to buy from B&H photo and have it shipped out to Japan. YOu'll have to pay about a 5% (goign up to 10% over the next few years) in duty charges, but it'll still be significantly cheaper unless you are buying anything released this year.
First off, I'm also in Okinawa, so こんにちは. I live in Isa, Ginowan.
If you have a FPO/APO box (which I assume you have access to, since you mentioned AAFES) you won't have to worry about duty fees, which leads me to my next point, ANYTHING camera related is cheaper, way cheaper online from Adorama or BH than AAFES or out on town. Plus better customer support. This is how I buy practically everything, as stuff is just too expensive here.
Be aware, that with at least Adorama, they won't send items that are over a certain dollar amount through USPS priority mail, which I'm sure you know is the only way to get things mailed here, quickly and relatively cheaply.
Since you have been here for 12 years and I only 8 months, I'm sure you know that are many fantastic locations to shoot at here.
Check out my Flickr (http://www.flickr.com/photos/ronspics12345/
) and this guys, whose live here for almost 40 years (http://www.flickr.com/photos/24443965@N08/
). Enjoy, and let me know if you ever wanted to get together as I can show how to operate that new 60D of yours. If you needed the advice of course.