the exposure bracketing is one way to make sure you get the right exposure. that is what i was going to suggest. as for the white balance, it is better to use something that is only 18% white, not all white. they sell custom white blance cards but i use a lid to a tupperware. i have read that the lid to a pringles can works well to.
here is a really good page on white balance: (http://www.cambridgeincolour.com/tut...te-balance.htm).
good luck! photography is as addicting as snakes!