It kind of depends which version of AI you have. In newer versions, you just paste the picture into a document, go to Window > Image Trace, and check "Preview". Then adjust the threshold until you get the effect you want.
If you can't get the result you're after (say, for example, that the nose gets washed out when the eyes look good or the eyes go black when the nose looks right) you'll have to use Photoshop.
The image has to be of a reasonable quality and size, or you just won't get the amount of detail you want.