" Do I need to cut existing granite? "

Yes.

" Is that easy to do? "

Not with the proper tools and equipment. But for a homeowner, quite difficult.

" Any suggestions with who to contact to install? "

A stone fabricator that kitchen counter tops.

I think this was Joe Corlett's company before he retired. If you aren't in FL, you need to find a similar company in your state. This shows you how it is done.

https://www.ihatemysink.com/

Just remember, Joe is a unicorn, not every company out there will be as good.

I know you want a farm style sink, but another option would be to replace the undermount sink you dislike with an undermount sink you do like, without cutting the counter top. It may not be what you have in mind, but it will be a great improvement. Just make sure the plumber uses a sink harness if possible.

"Do I need to cut existing granite?"

Yes.

"Is that easy to do?"

It's not a DIY project if you want an undermount sink. An intermediate DIY may be able to install a top mount apron sink. Kohler 3942.

"Any suggestions with who to contact to install?"

www.ihatemysink.com

You've apparently got a 36" sink base cabinet which means that you can have a 36" short apron front sink undermounted. I'd recommend a Kohler 3943 in stainless steel or an Elkay Quartz Luxe in composite.

This is such helpful feedback I am very thankful. Sounds like the farm style will be too much of a headache.