I did this recently, and it is very easy to do. I think I found a thread on the AF forum with real specific instructions (which I printed and took with me) that helped a lot. I've also found people on the ground at CDG are very happy to help. I was advised to walk rather than take a transfer bus. If you're not real careful, you can end up on the wrong bus, and it's not a safe bet that the drivers speak English, or even French, for that matter. It was a ten minute walk at most.