I am wondering which picel amout to buy for a web cam. I want it to be a web cam but a digital camera all i.

Pixel count isn't everything ... it's the quality of the lense and other components that determines the final quality of the photo's, as well as number of megapixels. Do some research online for "digital camera reviews" and see what you can find out about various brands. Trust me, you don't want any of the camera's sold for $150 or less. I would plan on spending $250, and only on one with good reviews.

All in one, eh?

What you need to worry about is the maximum you can get - at least 3 Megapixel for taking photos - preferably more.
And don't go for digital zoom - it is useless, you want optical zoom.

Then, for use as a webcam, you need to be able to configure various resolutions, ie bit-rates, to match the speed of the network access you or the person at the other end have.