Hi, i'm meeting someone through Craigslist to take a look & purchase his 430 EX II flash unit. Being a newbie, and not yet knowing how to use the controls of this thing, what can I do to "test" this unit out to hopefully ensure I am not buying a "lemon"? Please share any insights. Thanks very very much. it's reportedly in excellent condition, purchased last year from a reputable store in the area, has not been dropped, etc....But one can never know.....I'm a bit nervous, but the price is just right for me.