Lactose at the end of the boil, or for that matter any time in the boil, but if you add it at the beginning it will decrease your hop utilization.
For the chocolate I used unsweetened Hersey's bakers chocolate. The stuff the comes in powdered form. I would throw it in at the same time as the lactose though, the more time it gets to be in contact with the wort the better.
Not sure on the extract.
And yes, Senior at U of I