others have covered the correct full form, but to the issue of the pronunciation, it's not pronounced "would of" it's MISpronounced "would of". You can make any weird confusing pronunciation you want out of anything if you're willing to say it "wrong". The correct pronunciation of the contraction, as another hinted at is basically "would have" without the h and the a becoming an sound "uh" instead of an "ah" sound.
