Is the shield only a plate blocking the side (IC) and top or does it extend around and make more of a closed-in box for the turbo?
Makes somewhat of a box - but not completely. Covers top and 2 sides. Boxing it in fully doesn't allow for full air flow from the stock/aftermarket hood to circulate & cool shield/components.
EDIT: I took a look at the pic on the web page and it appears that the compressor portion is left outside the heat shield. This seems good to me!
Other question: does the mounting bolt/washer go through the extra hole (relative to stock) on the IC mounting bracket above the turbo?
Yes it does mount to a stock location. uses a 6mm Allen bolt with washer - both stainless of course and included.