1) Be careful.
2) Be careful.
That's with reference to flash art (i.e. the stuff on the walls that you point to and say I'll take that one).
If you don't know what it really says then chances are the tattoo artist doesn't either. I heard one story about someone who understood Japanese saw a list of japanese characters (might've been kanji) each meaning different things. One of them read "I'm so stupid I don't know what this means" - although obviously the notice said it was something different!
Apparently the tattoo artist said to the person he had already given that one to a bunch of people.
I do know a site where you can get some words translated for free by professional translators (so not altavista translate heh). I'll try and dig it out for you if you wish? Naturally we'd want to see pictures later.
Another option is going to say a chinese restaurant but you'd have to trust them! That option works better if you already have the design and want to double check it says what you think it does; that would be the safest way if you insisted on looking at a website that had lists of the characters.