1. Does it matter where you drill?
2. Can you deplete an area.
3. Can you find woohooium in intersecting tunnels or only in the major drilling opperation?
Oh and I gues a fourth... can you find woohooium by breaking space rocks?
1. It doesn't seem to matter, no.
2. You do finish a hole after a while, so that exact location is effectively depleted while the hole exists. However, you can fill the hole in and if you drill on the exact location, you'll continue to find things as you would if you had never drilled there.
3. I'm not exactly sure what you mean by this. Once a hole is "complete, it's effectively connected to any other hole you have drilled. To travel between them, all you have to do is name the tunnels.
4. You do not find any metals while breaking space rocks. Just gems. However, in addition to transfiguration (as mentioned by Chronic), you do find a lot of Woohooium by sculpting in stone. Make sure your sculptor does
not have the "Savvy Sculptor" trait, however, or they won't break statues while sculpting. It's really your best bet for finding it without transfiguration.