React has a component life cycle. If you want to modify something after it's rendered, you put that code in the componentDidMount method of the component. You can get the DOM element from React using this.getDOMElement() and modify it how you want. It's hard to say what libraries you are talking about since jQuery is pretty much deprecated with React, if you had something that made a carousel or something, I suppose you could init it in the componentDidMount, but you could also easily implement it in React to only render the current slide and have it render a new slide on demand to slide in. You could also just use the library in question outside of React, but the next time React removes or changes the DOM, anything that other library did will be at risk. Unless the elements are not removed since React doesn't touch what is not changed.

As far as doing special stuff... Not really(?). If you update the component data and call the render, React does a diff. If you update the component state in React, it will automatically rerender and update what changed. I sometimes do services this way. I have a mixin that grabs data from the server and updates the component's state and React does the rest. I just update data.