I am going to replace my countertop and sink, but the installer wants me to buy the sink first and then he will make the appropriate cut outs for it.  Then I will need a plumber to install it.

1. How do I know how to buy the right size sink so that my plumbing wont need major work?
2. Or, should I just buy whatever kitchen sink I like best and then have my plumber make adjustments?

Here are some pictures: <br>
![image description here][1]
![enter image description here][2]

  [1]: https://i.sstatic.net/Xulw9l.jpg
  [2]: https://i.sstatic.net/mBpzIl.jpg