Since you've tried the over the counter method, I would agree with Bobbi. Hire a pro. Those sinks are so pretty refinished to their original state and a pro will give you a finish that will last the rest of your life. If you can't find anyone listed in the phone book, ask around at a hardware store.

Stand, place your arms *straight* in front of you, as if they were in a sink, so ....a bit like you are ready to dive into a pool. Get someone to measure the height of your finger tips from the floor. This will be the height of the base inside your sink. Once you find the sink you want you'll know how deep your sink is and be able to work out how high to place it.

Take a very sharp pointed exact knife and remove the excess which is what is showing who ever installed sink should have done that.

I suggest you follow the step-by-step guide for creating storage cabinets under the bathroom sink. Take proper measurements - Measure the available available space in height, width and height. Cut Plywood to size - With a circular saw and framing square, cut all the required pieces out. You can use a sliding compound saw as an alternative. Attach the base and sides - Start assembling the sink cabinets by placing the bottom piece of plywood sheet on a flat surface. Attach the back and top boards - Place the plywood sheet for the top part of the cabinet and attach wood screws to connect it to both the sides. Turn the back faces of the cabinet upwards. Keep the back piece over the structure and fix it into place with wood screws. Attach shelves - Place the cabinet in an upright position to install the shelves. Slide a shelf into the structure so it is flush against the back. Attach door - Keep both hinges of the door on the same side of the plywood sheet. Drill them using wood screws into place. Now keep the door over the cabinet structure, extend the hinges to one of the side panels and fix them to make them secure. Fix a hasp closure on the other side of the door, placing it in the center of the hinges.