Throttle Body

Hi, I've recently had a problem of rough idling on my polo to which I was advised it would be an idea to change my throttle body, I've bought a new one for the car and was just wondering how simple it is to fit? Is it just a matter of unscrewing the four bolts and and taking it off then re fitting the new one and all should work fine? Also any other reasons why my polo is idling rough?

Many thanks.

James.