I'm planning on replacing a pretty old bathroom sink. The dimensions are 31"length x 18"depth. The problem is I can't find any self-rimming sink with those dimensions. After doing some searches, I have decided to replace the vanity top. But what exactly is a vanity top? That's just like a countertop right? I would still have to buy a sink and trim the vanity so that I can mount the sink onto the vanity right? Please someone help me clarify this. Also any new suggestion is greatly appreciated.