I am replacing my countertop and sink. How do I choose a new sink that fits my existing plumbing?
Plumbing for a sink is fairly standardized.  The only thing you need to worry about is if you get a significantly deeper sink which pushes you below your drain line.  Since you're also replacing the counter, there's no need to worry about finding a sink that will cover your existing sink area.

Edit: Looking at the picture, I think you've got a good several inches lower that you can go before you will run into any issues with the drain.  I believe I see flex lines which means the plumber doesn't even need to solder any connections.  Note, because you have electrical and plumbing so close down there, please be sure that this outlet is on a GFCI breaker.