As long as the mulch is 2" thick or less it won't hurt the roots
Be sure to pull it back from the trunk 6"
Yes, there is no evidence that fresh wood chips will leach nutrients from the soil or do any harm as long as they don't come in contact with the trunk, as Walter says.
Remembered reading this article a few weeks ago discussing mulches. It is a nice piece discussing mulches http://www.gardendesign.com/mulch-mistakes?cmpid=enews122711