I disconnected the drain line and simply unscrewed the bowl from the upper portion. I had to pry the upper portion out as it had some plumbers putty holding it down tight. That upper portion just drops in.
Don't replace it with the same bowl type, like some folks do. Go get a small drain at the hardware store with a basket and put it in. They come with a nut that scews on from underneath to pull it all together. Then just attach the drain line. That's what I did and also I purchased a small white rubber drain plug to seal the sink if I want to fill it wih water or keep things that are stored in the sink while traveling from going down the drain.
I love having the basket. The original drain didn't have one as it had a post with threads in center for the drain plug to screw into. That post was always in the way and hard to keep the drain clean.
I don't know why Scamp
every put that style drain in as it not necessary. The regular drains with baskets don't cost anymore and are certainly nicer. Oh, I know the bowl is intended to catch things like a trap but with a basket you don't worry about it.