I realize that no one else cares—except maybe Turbo if he ever reads this—but I am so pleased with my newfound skills at plumbing!
After buying the vent I mentioned earlier, I had to make several trips to the plumbing supply store to get the right PVC pipes. And I had to use my hacksaw on pipes too, because they only come in super-long pieces.
I found the purple primer and PVC cement that Turbo left in the bottom of my tool closet, and it was a stinky operation, but in the end I have an island sink drain that works like a charm and doesn't go glub, glub, glub.
I love when things go as planned.