Live trace is the hardest way to go. There are several 3rd party effects that do this kind of thing. Cartoon, included in AE will also do it. Trying to turn video frames or image sequences into live traced vector art is way more trouble than it is worth. Try searching for cartoon effect in the Search Help field at the top right corner of AE and check out the community resources for to learn how to use that effect.
Also check out: Red Giant | ToonIt
I downloaded it and ill give it a try, I still prefer the look of tracing though, it looks way less cheesy in my opinion.
Rotoscope or Rotobrush may be an option depending on your footage. To make autotrace work reliably you will probably have to heavily process your footage to reduce the number of colors and clean up edges. Motion blur and depth of field will cause you lots of problems.
If you go that way expect to spend a bunch more time than you would with a plug-in. Even the guys that did Scanner Darkly and walking life used software to process the footage instead of trying to auto trace the footage.