How Do I Care for Hair That is Dry and Frizzy, Yet Oily if Left Unwashed?

I have wavy hair and when it is clean it comes out wavy/straight, frizzy, and coarse to the touch (if left unstraightened). If I leave it unwashed for a day it's oily, greasy, limp and looks like I haven't taken a shower in a week. I dyed and highlighted my hair back in November of 2007, and have dyed my hair a couple times since then only to cover the highlights. In the picture my hair is greasy (I don't know if you can tell). This is only after about 36 hours without washing my hair. I'm getting married in January and this has prompted me to find a solution to my hair dillemma. How do I find a balance between the two?

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