Yahoo Japan is a bit odd.  You have to have a
"deputy" bid for you.  This is someone in Japan
who will bid on it for you, you send them the 
money and they ship you the cel.  I have not dealt
with Yahoo Japan myself, but tons of folks on this
board have and they can recommend good deputies to
you. :)  As for the dealers cels.org has links to,
I haven't had a bad experience with any of them
that I've dealt with personally.  One of my 
favorites is Anime Taro.  You do have to sign up
on the site, but once you do and you place an
order, everything is handled quickly and 
professionally.  The only dealer I've heard iffy
things about on this board is Mangaya and that was
a while ago, so that may be old business.  I hope
you have fun on  your cel collecting adventure! :)

Jen